WorldWideScience

Sample records for cleavage fracture

  1. Three-dimensional interpretation of cleavage fracture tests of cladded specimens with local approach to cleavage fracture

    International Nuclear Information System (INIS)

    Electricite de France has conducted during these last years an experimental and numerical research programme in order to evaluate fracture mechanics analyses used in nuclear reactor pressure vessels integrity assessment, regarding the risk of brittle fracture. Two cladded specimens made of ferritic steel A508 Cl3 with stainless steel cladding, and containing shallow subclad flaws, have been tested in four point bending at very low temperature to obtain cleavage failure. The crack instability was obtained in base metal by cleavage fracture, without crack arrest. The tests have been interpreted by local approach to cleavage fracture (Beremin model) using three-dimensional finite element computations. After the elastic-plastic computation of stress intensity factor KJ along the crack front, the probability of cleavage failure of each specimen is evaluated using m, σu Beremin model parameters identified on the same material. The failure of two specimens is conservatively predicted by both analyses. The elastic-plastic stress intensity factor KJ in base metal is always greater than base metal fracture toughness K1c. The calculated probabilities of cleavage failure are in agreement with experimental results. The sensitivity of Beremin model to numerical aspects is finally exposed. (orig.)

  2. Interrelation between local and global characteristics of cleavage fracture

    Czech Academy of Sciences Publication Activity Database

    Grishchenko, W.; Kotrechko, S.; Mamedov, S.; Zatsarna, O.; Dlouhý, Ivo

    Zurich : Trans Tech Publications, 2014 - (Šandera, P.), s. 221-224 ISBN 978-3-03785-934-6. ISSN 1013-9826. - (Key Engineering Materials. 592-593). [MSMF 7 - International Conference on Materials Structure and Micromechanics of Fracture /7./. Brno (CZ), 01.07.2013-03.07.2013] Institutional support: RVO:68081723 Keywords : local stress * fracture * cleavage * embrittlement * strength Subject RIV: JL - Materials Fatigue, Friction Mechanics

  3. Numerical modeling of ductile tearing effects on cleavage fracture toughness

    International Nuclear Information System (INIS)

    Experimental studies demonstrate a significant effect of specimen size, a/W ratio and prior ductile tearing on cleavage fracture toughness values (Jc) measured in the ductile-to-brittle transition region of ferritic materials. In the lower-transition region, cleavage fracture often occurs under conditions of large-scale yielding but without prior ductile crack extension. The increased toughness develops when plastic zones formed at the crack tip interact with nearby specimen surfaces which relaxes crack-tip constraint (stress triaxiality). In the mid-to-upper transition region, small amounts of ductile crack extension (often c-values. Previous work by the authors described a micromechanics fracture model to correct measured Jc-values for the mechanistic effects of large-scale yielding. This new work extends the model to also include the influence of ductile crack extension prior to cleavage. The paper explores development of the new model, provides necessary graphs and procedures for its application and demonstrates the effects of the model on fracture data sets for two pressure vessel steels (A533B and A515)

  4. Modelling of ductile and cleavage fracture by local approach

    International Nuclear Information System (INIS)

    This report describes the modelling of ductile and cleavage fracture processes by local approach. It is now well known that the conventional fracture mechanics method based on single parameter criteria is not adequate to model the fracture processes. It is because of the existence of effect of size and geometry of flaw, loading type and rate on the fracture resistance behaviour of any structure. Hence, it is questionable to use same fracture resistance curves as determined from standard tests in the analysis of real life components because of existence of all the above effects. So, there is need to have a method in which the parameters used for the analysis will be true material properties, i.e. independent of geometry and size. One of the solutions to the above problem is the use of local approaches. These approaches have been extensively studied and applied to different materials (including SA33 Gr.6) in this report. Each method has been studied and reported in a separate section. This report has been divided into five sections. Section-I gives a brief review of the fundamentals of fracture process. Section-II deals with modelling of ductile fracture by locally uncoupled type of models. In this section, the critical cavity growth parameters of the different models have been determined for the primary heat transport (PHT) piping material of Indian pressurised heavy water reactor (PHWR). A comparative study has been done among different models. The dependency of the critical parameters on stress triaxiality factor has also been studied. It is observed that Rice and Tracey's model is the most suitable one. But, its parameters are not fully independent of triaxiality factor. For this purpose, a modification to Rice and Tracery's model is suggested in Section-III. Section-IV deals with modelling of ductile fracture process by locally coupled type of models. Section-V deals with the modelling of cleavage fracture process by Beremins model, which is based on Weibulls

  5. Study of mechanism of cleavage fracture at low temperature

    Science.gov (United States)

    Chen, J. H.; Wang, G. Z.

    1992-02-01

    In this investigation, a series of crack opening displacement (COD) tests were carried out at several low temperatures for C-Mn weld steel. Some of the specimens were loaded until fracture, and the mechanical properties and microscopic parameters on fracture surfaces were measured. Other specimens were unloaded before fracture at different applied loads. The distributions of the elongated cavities and the cleavage microcracks ahead of fatigue crack tips were observed in detail. Based on the experimental results, the combined criterion of a critical strain ɛ p ≥ ɛc) for initiating a crack nucleus, a critical stress triaxiality (σ m/σ ≥ tc) for preventing it from blunting, and a critical normal stress (σ yy/σf) for the cleavage extension was proposed again, and the critical values of ɛp and σm/-σ for the C-Mn weld steel were measured. The reason why the minimum COD value could not be zero is explained. The mechanism of generation of the lower limit COD value on the lower shelf of the toughness transition curve is proposed.

  6. Review and perspective on approaches of evaluating cleavage fracture toughness of pressure vessel steels

    International Nuclear Information System (INIS)

    Although efforts have been made to establish cleavage fracture model in the past 30 years or so, uncertainties remain in predicting the cleavage fracture toughness behavior of reactor pressure vessel steels in the transition region. Confusions may be raised in cases such as that there are still outliers while ASME fracture toughness curve indexed to the reference temperature is generally considered as very conservative. The advantage and potentials of using Finite Element method to predict the cleavage fracture behavior of irradiated materials are obvious. However, its effectiveness depends on the rightness of the physical model and criteria established. In this paper, approaches of describing cleavage fracture toughness of pressure vessel steels in the transition region are discussed and compared. The need for focusing on the physical fundamental and criteria of cleavage fracture is addressed. (authors)

  7. Cleavage Fracture in a Ferritic Steel Weld: Characterization of Second Phase Particles

    OpenAIRE

    S. Schilling, N. Chapeau, A.P. Jivkov, E. Keim, S.R. Ortner, M.G. Burke

    2013-01-01

    Cleavage fracture can initiate by the cracking of second phase particles in metals. Understanding the size distribution, morphologies and compositions of initiating particles for a particular material is key to successful micromechanical modelling of cleavage. The second phase particles responsible for the fracture initiation in P141 CAC-S7, a reactor pressure vessel (RPV) weld metal from the EU-funded PERFORM 60 Multiscale Modelling Programme, have been identified and characterised in order ...

  8. Grain boundary effect on the nature of cleavage fracture in copper crystallite under pulsed loading

    International Nuclear Information System (INIS)

    The computer modeling of cleavage fracture in the copper crystallite, containing grain boundary under pulsed loading, is carried out. It is shown that tendency to material destruction along the grain boundary is increasing by initiation of packages of several isolated compression pulses (ICP) in the material. Increase in the ICP number in the package leads to the cleavage fracture along the boundaries, outlying over a great distance from the free surface. The cleaved fragments decompose with time into smaller ones due to growing spread of atomic velocities

  9. The shallow flaw effect and the local approach to cleavage fracture

    International Nuclear Information System (INIS)

    The purpose of this paper is to evaluate the capability of local approach (Beremin model developed in the past by Ecole des Mines de Paris) to explain the shallow flaw effect in cleavage fracture, i.e., significantly higher toughness in specimens with short cracks compared to classical specimens with deep cracks. Numerous two-dimensional finite element calculations are performed on several cracked specimens submitted to mechanical or thermal loading. The behavior of different specimens is examined using the Weibull stress σw versus stress intensity factor Kj curves. The comparison between different specimens shows significant differences, related to the a/W ratio. For a given level of the applied stress intensity factor, the probability of cleavage fracture evaluated with the Beremin model is higher on specimens containing deeper cracks. That means that, for a same probability of failure, higher fracture toughness must be obtained on specimens with shallow flaws. This comparison is completed by examining the evolution of stress fields and plastic zones at the crack tip during the loading. Significant differences are observed between each specimen. Those differences are well correlated with the a/W ratio. The effect of a/W ratio on the probability of cleavage fracture is underlined. These results can explain the increase of fracture toughness experimentally observed in different laboratories on specimens with shallow flaws. This study is relevant to fracture in reactor pressure vessels

  10. Critical cleavage fracture stress characterization of A508 nuclear pressure vessel steels

    International Nuclear Information System (INIS)

    The critical cleavage fracture stress of SA508 Gr.4N and SA508 Gr.3 low alloy reactor pressure vessel (RPV) steels was studied through the combination of experiments and finite element method (FEM) analysis. The results showed that the value of the local cleavage fracture stress, σF, of SA508 Gr.4N steel was significantly higher than that of SA508 Gr.3 steel. Detailed microstructural analysis was carried out using FEGSEM which revealed much smaller grains, finer and more homogenous carbide particles formed in SA508 Gr.4N steel. Compared with the SA508 Gr.3 steel currently used in the nuclear industry, the SA508 Gr.4N steel possesses higher strength and notch toughness as well as improved cleavage fracture behavior, and is considered a better candidate RPV steel for the next generation nuclear reactors. - Highlights: • Critical cleavage fracture stress was calculated through experiments and FEM. • Effects of both grain and carbide particle sizes on σF were discussed. • The SA508 Gr.4N steel is a better candidate for the next generation nuclear reactors

  11. An energy approach to predict cleavage fracture under non-proportional loading

    International Nuclear Information System (INIS)

    The paper provides an energy approach to predict cleavage fracture under non-proportional loading. It is based on an energy minimization and uses a notch model to represent the crack. An energy based cleavage criterion is defined. Validation is conducted in the context of two European programmes, showing that the approach accounts for both shallow crack and warm pre-stress effects. All these results are analyzed and discussed by referring to the classical Beremin model. This approach can be seen as a simple extension of the classical J approach, providing a tool of common and practical use for engineers. (authors)

  12. The effects of the local fracture stress and carbides on the cleavage fracture characteristics of Mn-Mo-Ni low alloy steels in the transition region

    International Nuclear Information System (INIS)

    In the ductile-brittle transition temperature region of SA508 C1.3 Mn-Mo-Ni low alloy steels, the relationship of the local fracture stress and carbides influencing the cleavage fracture behavior was investigated. Based on the ASTM E1921-97 standard method, the reference transition temperatures were determined by three point bending fracture toughness tests. A local fracture stress σf*, was determined from a theoretical stress distribution in front of crack tip using the cleavage initiation distance measured in each fractured specimen surface. The local fracture stress values showed a strong relationship with toughness characteristics of the materials and those were larger in the materials of smaller carbide size. Quantitative analysis of carbides showed that carbides larger than a certain size are mainly responsible for the cleavage fracture in the ductile-brittle transition temperature region. (author)

  13. Application of the local fracture stress model on the cleavage fracture of the reactor pressure vessel steels in the transition temperature region

    International Nuclear Information System (INIS)

    The fracture toughness in the ductile-brittle transition region of reactor pressure vessel steels was evaluated by means of an RKR-type model which describes the temperature dependence of the cleavage fracture toughness based on the constant fracture stress σf. The fracture stress σf and the characteristic distance are two main parameters in the RKR model. In order to apply the RKR model to the transition temperature region, these two parameters were investigated in different manners. In this study, the local fracture stress, σf*, was determined from the pre-cracked specimens. The results showed that the local fracture stress σf* determined from the pre-cracked specimens was higher than the fracture stress σf from the notched specimens, while those values were practically independent of the temperatures. The CID (cleavage initiation distance), which represents the distance from the crack tip to the cleavage initiation site, was measured in every fractured specimen. The measured CID values were strongly dependent on the test temperatures. Besides, the fracture toughness KJC in the transition region was dependent on the measured CID. The RKR model, when the local fracture stress σf* and the measured CIDs were applied, could describe the temperature dependency of the median transition fracture toughness KJC(med)

  14. The shallow flaw effect and the local approach to cleavage fracture

    International Nuclear Information System (INIS)

    The capability of Beremin model to explain the shallow flaw effect in cleavage fracture is evaluated. Numerous two-dimensional finite element calculations are performed on several cracked specimens (cladded and un-cladded specimens with different values of a/W ratio) submitted to mechanical or thermal loading. The behavior of different specimens is examined using the Weibull stress σw versus stress intensity factor KJ curves. The stress fields and plastic zones at the crack tip are also compared on respective cracked specimens. (K.A.)

  15. Understanding and accounting for the effects of residual stresses on cleavage fracture toughness measurements in the transition temperature regime

    International Nuclear Information System (INIS)

    Secondary self-balancing stresses exist in structural components due to manufacturing processes, e.g. welding. When a defect is present, such secondary stresses will influence both the local crack driving force and the level of crack-tip constraint. Fracture mechanics specimens machined from welded components can also retain significant residual stresses, and these can influence the measurement of fracture toughness. This paper describes the results of an experimental and numerical programme aimed as quantifying the effect of residual stresses on cleavage fracture toughness measured in deeply-cracked and shallow-cracked fracture mechanics specimens and with a view to correcting the resultant data. The results indicate that the influence of retained residual stresses on cleavage fracture toughness in such specimens can be characterised using two-parameter fracture mechanics. - Highlights: • The effect of residual stress on both crack driving force and crack-tip constraint has been examined. • Current guidance can generate non-conservative cleavage fracture toughness values where residual stresses are present. • The effects of residual stress on crack-tip constraint can be well characterised via two-parameter fracture mechanics. • Fracture toughness data acquired using laboratory specimens containing residual stresses could be corrected

  16. Local approach to strength mis-match effect on cleavage fracture of notched material

    International Nuclear Information System (INIS)

    This paper discusses the strength mis-match effect on cleavage fracture of notched materials based on the local approach. The aim of the study is to verify the independence of the critical Weibull stress at fracture on the strength mis-match condition. Diffusion bonded joints were made with two materials S and H different in strength level. Two types of 3-point bend specimen were extracted. One had a notch in the lower strength material S near the bonded interface, and another in the higher strength material H. Homogeneous specimens were also made for each material. The critical CTOD value at cleavage fracture for the overmatched specimen with a notch in the material S was smaller than that of the homogeneous specimen of the material S. By contrast, the undermatched specimen with a notch in the material H showed apparently larger critical CTOD value than the homogeneous specimen of the material H. The strength mis-match effect on the CTOD results was explained in terms of the constraint effect on the near-tip stress field. Namely, the near-tip stress is elevated by strength overmatching and relaxed by strength undermatching. The Weibull stresses for the homogeneous and mis-matched specimens were evaluated in the light of the near-tip stress fields. The critical Weibull stress at fracture did not depend on the strength mis-match condition near the notch. By using the critical Weibull stress obtained for the homogeneous specimen, the strength mis-match effect on the CTOD results can be predicted. Close agreement was observed between the critical CTOD value predicted and that obtained by the experiment. (orig.)

  17. Determination of cleavage planes and fracture characterization of Ni-based single crystal superalloys

    Science.gov (United States)

    Merrill, John M.; Wilcox, Roy C.

    1992-01-01

    The room temperature fracture behavior of the Ge Rene N-4, CMSX-2, and CMSX-4C single crystal Ni-based superalloys was studied. All crystals were grown along the (001) direction and tensile tested in both helium and hydrogen atmospheres. A stereoscopic technique developed for use with a scanning electron microscope was applied to determine cleavage planes. Planar gamma(') morphologies also were examined to help determine cleavage planes. Helium charged specimens failed on a number of planes including the (111), (110), and (320). In most cases planes of the (111)-type initiated at the notch region and became smaller and smaller as they moved in radially. Tensile strengths in helium averaged 1000 MPa higher than that of the hydrogen charged specimens. Specimens tested in hydrogen generally failed on (100)-type planes originating from the notch region. This (100) region comprised 60 to 80 percent of the total fracture surface on most samples and appeared as large flat planes perpendicular to the growth direction of the crystal. The interior regions contained (100)-type planes as well as (321), (320), (210), and (111)-types. Hydrogen charged specimens also showed a high percentage of large cracks oriented at 90 deg to one another, indicative of the (100)-type fracture. The Ge Rene N4 and the CMSX-4C samples contained 3-5 percent gamma/gamma(') eutectic, while the CMSX-2 samples had little or no gamma/gamma(') eutectic. The relationship between gamma/gamma(') eutectic and the fracture surface has not been fully determined, but it is thought that the gamma/gamma(') eutectic may serve as a possible trapping site for hydrogen.

  18. Elements of a fracture mechanics concept for the cleavage fracture behaviour of RAFM steels using local fracture criteria. Final report for task TW1-TTMS-005/D3

    International Nuclear Information System (INIS)

    An effort is made within the European Fusion Technology Programme framework to obtain a fracture mechanics description of the material behaviour in the ductile to brittle transition-regime using local fracture criteria. This report summarizes the necessary procedural steps towards the development of an according design code scheme. It makes heavy use of available code schemes such as the British Energy R6-Code or the ESIS P6 procedure and specializes in application to the class of low activation materials that are envisaged for ITER. Through an integrated approach using a numerical stress analysis at experimentally observed fracture loads of notched tensile specimens, a statistical evaluation of cleavage fracture parameters can be performed. The report contains a description of the necessary steps for the experimental characterization and the numerical analysis as well as results for the two RAFM steel variants F82Hmod and EUROFER 97 which serve as basis for the verification of the method. Statistical inference methods are addressed as well as fractographic investigations that are essential for the verification of the approach via numerical prediction of the fracture origin distribution. Limits of the current methodology are given and topics of future research are indicated. (orig.)

  19. Status report on experiments and modelling of the cleavage fracture behaviour of F82Hmod using local fracture grid. Task TTMS-005

    International Nuclear Information System (INIS)

    Within the European Fusion Technology Programme framework, a fracture mechanics description of the material behaviour in the ductile to brittle transition-regime is developed using local fracture criteria. Based on experimental results using axisymmetrically notched and pre-cracked specimens together with a numerical stress analysis at fracture load, a statistical evaluation of cleavage fracture parameters can be performed along the lines described in various code schemes such as the British Energy R6-Code or the ESIS P6 procedure. The report contains results of the experimental characterization of the deformation and fracture behaviour of the fusion candidate RAFM steel variant F82Hmod, details and background of the numerical procedure for cleavage fracture parameter determination as well as additional statistical inference methods for transferability analysis. Fractographic results give important information about fracture mode and fracture origin sites and their location. Numerical prediction of fracture origin distribution is an important tool for transferability assessment. Future issues comprise constraint effect and ductile damage as well as incorporation of irradiation effects, which are topically addressed. The methodology developed and described in the present report will be applied to characterize material behaviour of future RAFM variants as the EUROFER 97, for which analysis is currently under way. (orig.)

  20. The application of local approach to assess the influence of in-plane constraint on cleavage fracture

    International Nuclear Information System (INIS)

    The assessment of real or postulated flaws within critical components is conventionally carried out using methods based on single parameter fracture mechanics. For low constraint configurations (e.g. shallow cracks) such methods can provide highly conservative assessments. Two-parameter (J-T, J-Q) fracture mechanics has been developed to quantify the influence of crack-tip constraint on fracture and this development has been incorporated into a modified R6 framework to reduce the conservatisms associated with the assessment of low constraint configurations. This framework requires that the constraint of the structure is quantified (with respect to T or Q) and that the materials fracture response to constraint is measured by testing a number of cracked specimens which sample a range of constraint levels. An alternative method of assessment, which may be used in situations where fracture data are unavailable over the full range of constraint, is the so-called local approach to fracture. In this Paper, the local approach has been used alongside the modified R6 framework to assess the cleavage fracture behavior of a well characterized mild steel plate at -50 C. The local approach method predicts: (i) an upswing in cleavage fracture toughness as a function of decreasing crack-tip constraint which is conservative with respect to the actual materials response, (ii) an increase in the scatter of cleavage fracture toughness as a function of decreasing crack-tip constraint. This is a direct consequence of framing the local approach model within two-parameter Weibull statistics. Finally it is shown that the local approach may be used successfully alongside the modified R6 framework to assess low constraint geometries: resultant failure assessment curves reduce the conservatism of the conventional Option 1 curve

  1. Approximate techniques for predicting size effects on cleavage fracture toughness (Jc)

    International Nuclear Information System (INIS)

    This investigation examines the ability of an elastic T-stress analysis coupled with modified boundary layer (MBL) solution to predict stresses ahead of a crack tip in a variety of planar geometries. The approximate stresses are used as input to estimate the effective driving force for cleavage fracture (J0) using the micromechanically based approach introduced by Dodds and Anderson. Finite element analyses for a wide variety of planar cracked geometries are conducted which have elastic biaxiality parameters (β) ranging from -0.99 (very low constraint) to +2.96 (very high constraint). The magnitude and sign of β indicate the rate at which crack-tip constraint changes with increasing applied load. All results pertain to a moderately strain hardening material (strain hardening exponent (η) of 10). These analyses suggest that β is an effective indicator of both the accuracy of T-MBL estimates of J0 and of applicability limits on evolving fracture analysis methodologies (i.e. T-MBL, J-Q, and J/J0). Specifically, when 1β1>0.4 these analyses show that the T-MBL approximation of J0 is accurate to within 20% of a detailed finite-element analysis. As ''structural type'' configurations, i.e. shallow cracks in tension, generally have 1β1>0.4, it appears that only an elastic analysis may be needed to determine reasonably accurate J0 values for structural conditions

  2. The effects of strength and geometry on cleavage fracture stress and strain limits of martensitic stainless steels

    International Nuclear Information System (INIS)

    A two-parameter procedure (TPP) for evaluating cleavage fracture stresses was investigated. The TPP interpolates between linear elastic and fully plastic fracture regimes. Predictions of the TPP were compared to experimental data obtained from bend bars 0.5 to 2.0 cm wide with various crack-to-width ratios, at -730C and -1010C, and at three displacement rates. Agreement was good. The results suggest that thin-walled components containing shallow cracks will fail near plastic collapse stresses. In such a case, irradiation would probably result in an increase in the fracture stresses. Bend ductilities were low and found to be very sensitive to geometry and strength level. (orig.)

  3. The effects of strength and geometry on cleavage fracture stress and strain limits of martensitic stainless steels

    Science.gov (United States)

    Odette, G. R.; Lucas, G. E.; Maiti, R.; Sheckherd, J. W.

    1985-08-01

    A two-parameter procedure (TTP) for evaluating cleavage fracture stresses was investigated. The TPP interpolates between linear elastic and fully plastic fracture regimes. Predictions of the TPP were compared to experimental data obtained from bend bars 0.5 to 2.0 cm wide with various crack-to-width ratios, at -73°C and -101°C, and at three displacement rates. Agreement was good. The results suggest that thin-walled components containing shallow cracks will fail near plastic collapse stresses. In such a case, irradiation would probably result in an increase in the fracture stresses. Bend ductilities were low and found to be very sensitive to geometry and strength level.

  4. Confocal microscopy-fracture reconstruction and finite element modeling characterization of local cleavage toughness in a ferritic/martensitic steel in subsized Charpy V-notch impact tests

    International Nuclear Information System (INIS)

    The confocal microscopy (CM)-fracture reconstruction (FR) method, coupled with scanning electron microscopy (SEM) fractography, was used to measure the critical notch deformation conditions at cleavage initiation for two subsized Charpy V-notch (CVN) specimen geometries of Japan ferritic/martensitic steel (JFMS). A new method was developed to permit FR of notched specimens. Three-dimensional finite element analysis (FEA) simulations of the notch and specimen deformation were used to estimate values of critical micro-cleavage fracture stress, σ*, and critical stressed area, A*. Since σ*-A* is independent of size and geometry, it provides a fundamental local measure of cleavage toughness

  5. Investigation on the evaluation of cleavage fracture toughness using PCCv specimens in the ductile-brittle transition range of reactor pressure vessel steels (contract research)

    Energy Technology Data Exchange (ETDEWEB)

    Onizawa, Kunio; Tobita, Tohru; Suzuki, Masahide [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-11-01

    To obtain a reliable fracture toughness value for the cleavage fracture initiation in the ductile-brittle transition range of RPV steels, the applicability of precracked Charpy-v (PCCv) specimens was investigated. An approach based on the weakest link theory and fractographic observation were applied to analyze the specimen size effect and the scatter of fracture toughness values. The materials used were four kinds of ASTM A533B class 1 steels that were all manufactured by Japanese steel makers. The specimen size effect on cleavage fracture toughness was seen between PCCv and 1T-CT specimens. To obtain the equivalent data from PCCv specimens to 1T-CT specimens, the size correction scheme based on the weakest link theory was applied to the PCCv data. However, it was found that the size effect was still remained to some extent. The fracture toughness transition curve was evaluated by means of the master curve approach which was being proposed by the ASTM. The master curve determined by PCCv data tended to overestimate the fracture toughness at the upper transition range where PCCv data would be invalid. According to the master curve approach using valid PCCv data sets, it was shown that the shift of the master curve by irradiation was somewhat greater than the Charpy 41J shift. Through fractographic observation, the ductile crack growth before a cleavage fracture was characterized and the initiation site of cleavage fracture was determined. (author)

  6. Development of a Weibull model of cleavage fracture toughness for shallow flaws in reactor pressure vessel material

    International Nuclear Information System (INIS)

    A primary objective of the United States Nuclear Regulatory Commission (USNRC) -sponsored Heavy-Section Steel Technology (HSST) Program is to develop and validate technology applicable to quantitative assessments of fracture prevention margins in nuclear reactor pressure vessels (RPVs) containing flaws and subjected to service-induced material toughness degradation. This paper describes an experimental/analytical program for the development of a Weibull statistical model of cleavage fracture toughness for applications to shallow surface-breaking and embedded flaws in RPV materials subjected to multi-axial loading conditions. The experimental part includes both material characterization testing and larger fracture toughness experiments conducted using a special-purpose cruciform beam specimen developed by Oak Ridge National Laboratory for applying biaxial loads to shallow cracks. Test materials (pressure vessel steels) included plate product forms (conforming to ASTM A533 Grade B Class 1 specifications) and shell segments procured from a pressurized-water reactor vessel intended for a nuclear power plant. Results from tests performed on cruciform specimens demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower-transition temperature region. A local approach methodology based on a three-parameter Weibull model was developed to correlate these experimentally-observed biaxial effects on fracture toughness. The Weibull model, combined with a new hydrostatic stress criterion in place of the more commonly used maximum principal stress in the kernel of the Weibull stress integral definition, is shown to provide a scaling mechanism between uniaxial and biaxial loading states for 2-dimensional flaws located in the A533-B plate material. The Weibull stress density was introduced as a matrice for identifying regions along a semi-elliptical flaw front that have a higher probability of cleavage initiation. Cumulative

  7. Further application of the cleavage fracture stress model for estimating the T0 of highly embrittled ferritic steels

    International Nuclear Information System (INIS)

    The semi-empirical cleavage fracture stress model (CFS), based on the microscopic cleavage fracture stress, sf, for estimating the ASTM E1921 reference temperature (T0) of ferritic steels from instrumented impact testing of unprecracked Charpy V-notch specimens is further confirmed by test results for additional steels, including steels highly embrittled by thermal aging or irradiation. In addition to the ferrite-pearlite, bainitic or tempered martensitic steels (which was examined earlier), acicular or polygonal ferrite, precipitation-strengthened or additional simulated heat affected zone steels are also evaluated. The upper limit for the applicability of the present CFS model seems to be T41J ∝160 to 170 C or T0 or TQcfs (T0 estimate from the present CFS model) ∝100 to 120 C. This is not a clear-cut boundary, but indicative of an area of caution where generation and evaluation of further data are required. However, the present work demonstrates the applicability of the present CFS model even to substantially embrittled steels. The earlier doubts expressed about TQcfs becoming unduly non-conservative for highly embrittled steels has not been fully substantiated and partly arises from the necessity of modifications in the T0 evaluation itself at high degrees of embrittlement suggested in the literature.

  8. Further application of the cleavage fracture stress model for estimating the T{sub 0} of highly embrittled ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Sreenivasan, P.R.

    2016-02-15

    The semi-empirical cleavage fracture stress model (CFS), based on the microscopic cleavage fracture stress, s{sub f}, for estimating the ASTM E1921 reference temperature (T{sub 0}) of ferritic steels from instrumented impact testing of unprecracked Charpy V-notch specimens is further confirmed by test results for additional steels, including steels highly embrittled by thermal aging or irradiation. In addition to the ferrite-pearlite, bainitic or tempered martensitic steels (which was examined earlier), acicular or polygonal ferrite, precipitation-strengthened or additional simulated heat affected zone steels are also evaluated. The upper limit for the applicability of the present CFS model seems to be T{sub 41J} ∝160 to 170 C or T{sub 0} or T{sub Qcfs} (T{sub 0} estimate from the present CFS model) ∝100 to 120 C. This is not a clear-cut boundary, but indicative of an area of caution where generation and evaluation of further data are required. However, the present work demonstrates the applicability of the present CFS model even to substantially embrittled steels. The earlier doubts expressed about T{sub Qcfs} becoming unduly non-conservative for highly embrittled steels has not been fully substantiated and partly arises from the necessity of modifications in the T{sub 0} evaluation itself at high degrees of embrittlement suggested in the literature.

  9. Effects of Dynamic Strain Hardening Exponent on Abnormal Cleavage Fracture Occurring During Drop Weight Tear Test of API X70 and X80 Linepipe Steels

    Science.gov (United States)

    Kang, Minju; Kim, Hyunmin; Lee, Sunghak; Shin, Sang Yong

    2014-02-01

    In this study, drop weight tear tests (DWTT) were conducted on API X70 and X80 linepipe steels fabricated with various compositions and rolling and cooling conditions in order to correlate the strain hardening with the abnormal cleavage fracture occurring in the hammer-impacted area. Area fractions of fracture modes were measured from fractured DWTT specimens, and the measured data were analyzed in relation to microstructures, Charpy impact energy, and strain hardening. All the steels consisted of fine acicular ferrite, together with some bainitic ferrite, granular bainite, and martensite-austenite constituent. As the volume fraction of acicular ferrite increased, the area fraction of DWTT abnormal cleavage fracture decreased because the toughness of acicular ferrite was higher than other microstructures. The area fraction of abnormal cleavage fracture was weakly related with strain hardening exponents obtained from the quasi-static tensile and compressive tests, but showed better correlation with those obtained from the dynamic compressive test. This tendency could be more clearly observed when steels having similar Charpy impact energy levels were grouped. Since the DWTT was performed under a dynamic loading condition, thus, the abnormal cleavage fracture behavior should be related with the strain hardening analyzed under a dynamic loading condition.

  10. Effect of crystallographic texture on the cleavage fracture mechanism and effective grain size of ferritic steel

    International Nuclear Information System (INIS)

    The effect of crystallographic texture on impact transition behavior has been studied in a low-carbon steel. Crystallographic texture was found to influence the general yield temperature through its effect on the plastic constraint factor. The effective grain size depends on the angle between the {001} cleavage planes of the neighbouring crystals, rather than the grain boundary misorientation angle as determined from electron backscattered diffraction analysis considering the angle–axis pair

  11. Cleavage Fracture in Ferritic Steel Weld: Characterization of second phase particles

    OpenAIRE

    Andrey Jivkov, E Keim, MG Burke, N Chapeau, S Ortner, S Schilling

    2013-01-01

    Exposure of Alloy 82 welds to hydrogen containing, de-oxygenated aqueous environment at temperatures below 150C can result in a reduction of fracture toughness. The observed embrittlement has typically been related to hydrogen atoms trapped at intergranul

  12. Mechanisms and modeling of cleavage fracture in simulated heat-affected zone microstructures of a high-strength low alloy steel

    Science.gov (United States)

    Lambert-Perlade, A.; Sturel, T.; Gourgues, A. F.; Besson, J.; Pineau, A.

    2004-03-01

    The effect of the welding cycle on the fracture toughness properties of high-strength low alloy (HSLA) steels is examined by means of thermal simulation of heat-affected zone (HAZ) microstructures. Tensile tests on notched bars and fracture toughness tests at various temperatures are performed together with fracture surface observations and cross-sectional analyses. The influence of martensite-austenite (M-A) constituents and of “crystallographic” bainite packets on cleavage fracture micromechanisms is, thus, evidenced as a function of temperature. Three weakest-link probabilistic models (the “Master-curve” (MC) approach, the Beremin model, and a “double-barrier” (DB) model) are applied to account for the ductile-to-brittle transition (DBT) fracture toughness curve. Some analogy, but also differences, are found between the MC approach and the Beremin model. The DB model, having nonfitted, physically based scatter parameters, is applied to the martensite-containing HAZ microstructures and gives promising results.

  13. Cleavage Fracture of Brittle Semiconductors from the Nanometer to the Centimeter Scale

    OpenAIRE

    Wasmer, Kilian; Ballif, Christophe; Gassilloud, Rémy; Pouvreau, Cédric; Rabe, Rodolfo; Michler, Johann; Breguet, Jean-Marc; Solletti, Jean-Marie; Karimi, Ayat; Schulz, Daniel; Schulz, D; Wasmer, K; Ballif, C.; Pouvreau, C.; Rabe, R.

    2005-01-01

    The objective of this paper is to present the fundamental phenomena occurring during the scribing and subsequent fracturing process usually performed when preparing surfaces of brittle semiconductors. In the first part, an overview of nano-scratching experiments of different semiconductor surfaces (InP, Si and GaAs) is given. It is shown how phase transformation can occur in Si under a diamond tip, how single dislocations can be induced in InP wafers and how higher scratching load of GaAs waf...

  14. Cleavage Fracture Modeling of Pressure Vessels under Transient Thermo-Mechanical Loading

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Xudong [National University of Singapore; Dodds, Robert [University of Illinois; Yin, Shengjun [ORNL; Bass, Bennett Richard [ORNL

    2008-02-01

    The next generation of fracture assessment procedures for nuclear reactor pressure vessels (RPVs) will combine nonlinear analyses of crack-front response with stochastic treatments of crack size, shape, orientation, location, material properties and thermal-pressure transients. The projected computational demands needed to support stochastic approaches with detailed 3-D, nonlinear stress analyses of vessels containing defects appear well beyond current and near-term capabilities. In the interim, 2-D models become appealing to approximate certain classes of critical flaws in RPVs, and have computational demands within reach for stochastic frameworks. The present work focuses on the capability of 2-D models to provide values for the Weibull stress fracture parameter with accuracy comparable to those from very detailed 3-D models. Weibull stress approaches provide one route to connect nonlinear vessel response with fracture toughness values measured using small laboratory specimens. The embedded axial flaw located in the RPV wall near the cladding-vessel interface emerges from current linear-elastic, stochastic investigations as a critical contributor to the conditional probability of initiation. Three different types of 2-D models reflecting this configuration are subjected to a thermal-pressure transient characteristic of a critical pressurized thermal shock event. The plane-strain, 2-D models include: the modified boundary layer (MBL) model, the middle tension (M(T)) model, and the 2-D RPV model. The 2-D MBL model provides a high quality estimate for the Weibull stress but only in crack-front regions with a positive T-stress. For crack-front locations with low constraint (T-stress < 0), the M(T) specimen provides very accurate Weibull stress values but only for pressure load acting alone on the RPV. For RPVs under a combined thermal-pressure transient, Weibull stresses computed from the 2-D RPV model demonstrate close agreement with those computed from the

  15. Verification of a fracture mechanics concept for the cleavage fracture behaviour of RAFM steels using local fracture criteria. Final report for task TW2-TTMS-005/D3

    International Nuclear Information System (INIS)

    An effort is made within the European Fusion Technology Programme framework to obtain a fracture mechanics description of the material behaviour in the ductile to brittle transition-regime using local fracture criteria. In a companion report, the necessary procedural steps towards the development of an according design code scheme were described. The present report contains application examples and verification results of the different procedural steps and identifies limitations of the approach for the two reference RAFM steels F82Hmod and EUROFER97. (orig.)

  16. Cleavage behaviors in nuclear vessel steels

    International Nuclear Information System (INIS)

    Cleavage behaviors of nuclear vessel steels in the transition temperature range are reviewed. Viewpoints are presented to assist understanding of cleavage crack speed, cleavage initiation, cleavage arrest, and the sensitivity of fracture toughness to constraint and temperature. The importance of high local stress elevations by high strain rate is emphasized. This report is designated as HSST Report No. 149

  17. Cleavage Fracture Initiation at M-A Constituents in Intercritically Coarse-Grained Heat-Affected Zone of a HSLA Steel

    Science.gov (United States)

    Mohseni, Peyman; Solberg, Jan Ketil; Karlsen, Morten; Akselsen, Odd Magne; Østby, Erling

    2014-01-01

    Local brittle zones, i.e., martensite-austenite (M-A) islands, are formed within the coarse-grained heat-affected zone (CGHAZ) and the intercritically reheated CGHAZ (ICCGHAZ) during welding of many HSLA steels. In the current study, the M-A constituents in the microstructure of simulated ICCGHAZ of an API X80 pipeline steel were investigated using transmission electron microscopy and scanning electron microscopy. The focused ion beam technique was applied to make TEM specimens of M-A constituents that were located in the initiation sites of cleavage cracks. The main purpose of the study was to identify crack-initiation sites of cleavage fracture in ICCGHAZ and to prove the presence of M-A constituents in such initiation sites. Twinned martensite was detected in all local brittle zones that were investigated in the current study, demonstrating that they are M-A constituents. It was also demonstrated that the fracture initiation occurred preferentially at M-A constituents by a debonding mechanism rather than cracking of the M-A constituents.

  18. Effect of morphology of eutectic silicon crystals on mechanical properties and cleavage fracture toughness of AlSi5Cu1 alloy

    Directory of Open Access Journals (Sweden)

    M. Wierzbińska

    2005-12-01

    Full Text Available Purpose: The purpose of this paper is presentation of the results that concerned the influence of morphology of eutectic silicon crystals on mechanical properties, especially on the cleavage fracture toughness of AlSi5Cu1 alloy.Design/methodology/approach: Microscopic studies – optical microscope NIKON 300 and quantitative analysis of geometrical parameters of microstructure – image analysis program APHELION, tensile and fracture toughness tests – testing machine INSTRON 8810.Findings: The sizes of silicon crystals and values of yield strength, tensile strength and plane strain fracture toughness have been determined. Relationships between mechanical properties and silicon crystals size were described using Hall-Petch equation. It was found that a decrease in silicon crystals causes an increasing in strength and in fracture toughness.Practical implications: This paper is part of the previous author’s investigations which results in modification of the casting technology of turboblower compressor impellers.Originality/value: The microscopic observations indicated that alloy cracking begins with nucleation and growth of micro-cracks in the silicon crystals of large size, in orthogonal plane to tension direction. The hard and brittle silicon crystals are very strong barriers for slip in the stressed alloy.

  19. Fracto—emissions in Catastrophic Cleavage Process

    Institute of Scientific and Technical Information of China (English)

    HonglaiTAN; WeiYANG

    1996-01-01

    Fracto-emissions accompanying crack propagation are observed in the recent experiments.The energy impulses during and after fracture stimulate the fracto-emissions.Model concerning atomic scale cleavage processes is proposed to formulate a catastrophic fracure theory relevant to these phenomena.A criterion for catastrophic jump of the cleavage potential is applied to representative crystals.

  20. Microstructure and cleavage in lath martensitic steels

    International Nuclear Information System (INIS)

    In this paper we discuss the microstructure of lath martensitic steels and the mechanisms by which it controls cleavage fracture. The specific experimental example is a 9Ni (9 wt% Ni) steel annealed to have a large prior austenite grain size, then examined and tested in the as-quenched condition to produce a relatively coarse lath martensite. The microstructure is shown to approximate the recently identified ‘classic’ lath martensite structure: prior austenite grains are divided into packets, packets are subdivided into blocks, and blocks contain interleaved laths whose variants are the two Kurjumov–Sachs relations that share the same Bain axis of the transformation. When the steel is fractured in brittle cleavage, the laths in the block share {100} cleavage planes and cleave as a unit. However, cleavage cracks deflect or blunt at the boundaries between blocks with different Bain axes. It follows that, as predicted, the block size governs the effective grain size for cleavage. (paper)

  1. Fractures

    Science.gov (United States)

    ... commonly happen because of car accidents, falls, or sports injuries. Other causes are low bone density and osteoporosis, which cause weakening of the bones. Overuse can cause stress fractures, which are very small cracks in the ...

  2. Cleavage crystallography of liquid metal embrittled aluminum alloys

    Science.gov (United States)

    Reynolds, A. P.; Stoner, G. E.

    1991-01-01

    The crystallography of liquid metal-induced transgranular cleavage in six aluminum alloys having a variety of microstructures has been determined via Laue X-ray back reflection. The cleavage crystallography was independent of alloy microstructure, and the cleavage plane was 100-plane oriented in all cases. It was further determined that the cleavage crystallography was not influenced by alloy texture. Examination of the fracture surface indicated that there was not a unique direction of crack propagation. In addition, the existence of 100-plane cleavage on alloy 2024 fracture surfaces was inferred by comparison of secondary cleavage crack intersection geometry on the 2024 surfaces with the geometry of secondary cleavage crack intersections on the test alloys.

  3. Fracture Phenomena in Amorphous Selenium

    DEFF Research Database (Denmark)

    Lindegaard-Andersen, Asger; Dahle, Birgit

    1966-01-01

    Fracture surfaces of amorphous selenium broken in flexure at room temperature have been studied. The fracture velocity was found to vary in different regions of the fracture surface. Peculiar features were observed in a transition zone between fast and slower fracture. In this zone cleavage steps...

  4. Cleavage of nucleic acids

    Energy Technology Data Exchange (ETDEWEB)

    Prudent, James R. (Madison, WI); Hall, Jeff G. (Madison, WI); Lyamichev, Victor L. (Madison, WI); Brow, Mary Ann D. (Madison, WI); Dahlberg, James E. (Madison, WI)

    2007-12-11

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof.

  5. Cleavage of nucleic acids

    Energy Technology Data Exchange (ETDEWEB)

    Prudent, James R. (Madison, WI); Hall, Jeff G. (Waunakee, WI); Lyamichev, Victor I. (Madison, WI); Brow; Mary Ann D. (Madison, WI); Dahlberg, James E. (Madison, WI)

    2010-11-09

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof.

  6. Cleavage of nucleic acids

    Science.gov (United States)

    Prudent, James R.; Hall, Jeff G.; Lyamichev, Victor I.; Brow, Mary Ann D.; Dahlberg, James E.

    2000-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof.

  7. Mezzo-scopic Analysis of Fracture Toughness in Steels

    Directory of Open Access Journals (Sweden)

    Miyata Takashi

    2002-01-01

    Full Text Available The cleavage fracture toughness of steels was mezzo-scopically analyzed on the basis of the statistical local fracture criterion approach. The statistical stress criterion at the crack tip region suggests that the cleavage fracture toughness in steels can be described as a function of the yield stress, the cleavage fracture stress, and other mechanical properties of the materials. Formulation of the cleavage fracture toughness was first examined through an investigation on correlation between the cleavage toughness and the cleavage fracture stress obtained in notched round bar specimens in accordance with the theoretical prediction. Then, the scatter of the toughness, specimen thickness effect on the toughness, deterioration of the toughness due to cold working and irradiation, and improvement of the toughness caused by the Ni addition, were analyzed through the formulation of the toughness.

  8. Physical fracture properties (fracture surfaces as information sources; crackgrowth and fracture mechanisms; exemples of cracks)

    International Nuclear Information System (INIS)

    Fracture surfaces are considered as a useful source of informations: an introduction to fractography is presented; the fracture surface may be observed through X ray microanalysis, and other physical methods such as Auger electron spectroscopy or secundary ion emission. The mechanisms of macroscopic and microscopic crackgrowth and fracture are described, in the case of unstable fracture (cleavage, ductile with shear, intergranular brittleness) and of progressive crack propagation (creep, fatigue). Exemples of cracks are presented in the last chapter

  9. Cleavage of silicon by laser-based shock waves: Interpretation by nanoscopic length scales

    International Nuclear Information System (INIS)

    Cleavage along the weakest Si{1 1 1} cleavage plane is measured by impulsive fracture using surface acoustic waves (SAWs) with steep shock fronts, generated by pulsed laser irradiation and recorded with a laser probe–beam-deflection setup. The theoretical cleavage strength, obtained by ab initio calculations for perfect single-crystal silicon lattices is compared with the strength resulting from an improved Polanyi–Orowan cleavage model. The critical strength of a real silicon crystal, measured by using calibrated elastic surface pulses with shocks, was employed to extract the corresponding critical length scale characterizing the cleavage process on the basis of the modified cleavage model. The extracted length scale of 7 nm can be connected with the size of the microstructural defect initiating failure. Usually stress generating surface defects are responsible for the nucleation of brittle fracture, especially in nanoscale systems with large surface areas.

  10. Fracture mechanics safety approaches

    International Nuclear Information System (INIS)

    Component integrity assessments require the knowledge of reliable fracture toughness parameters characterising the initiation of the failure process in the whole relevant temperature range. From a large number of fracture mechanics tests a statistically based procedure was derived allowing to quantify the initiation of fracture toughness as a function of temperature as a closed function as well as the temperature dependence of the cleavage instability parameters. Alternatively to the direct experimental determination one also can use a correlation between fracture toughness and notch impact energy. (orig.)

  11. Fracture mechanics safety approaches

    Energy Technology Data Exchange (ETDEWEB)

    Roos, E.; Schuler, X.; Eisele, U. [Materials Testing Inst. (MPA), Univ. of Stuttgart (Germany)

    2004-07-01

    Component integrity assessments require the knowledge of reliable fracture toughness parameters characterising the initiation of the failure process in the whole relevant temperature range. From a large number of fracture mechanics tests a statistically based procedure was derived allowing to quantify the initiation of fracture toughness as a function of temperature as a closed function as well as the temperature dependence of the cleavage instability parameters. Alternatively to the direct experimental determination one also can use a correlation between fracture toughness and notch impact energy. (orig.)

  12. Initiation of cleavage in a low alloy steel: effect of a ductile damage localized around inclusions

    International Nuclear Information System (INIS)

    The fracture mechanism in a low alloy steel, used in the pressurised water reactor vessel, has been studied in the ductile to brittle transition temperature range. We used the local approach of fracture in conjunction with both fractographic observations and numerical simulations. Previous studies suggested the onset of cleavage to be favoured by the presence of nearby manganese sulphide (MnS) clusters: the ductile damaged zone localised inside a cluster increases the stress around it, and so contribute to the triggering of cleavage due to nearby classical sites, like carbides. The experimental study of size dependence and anisotropy on the global fracture behaviour, together with fractographic observations, give here the proof of the influence of MnS clusters on the onset of cleavage in this steel. Fracture behaviour of pre-cracked specimens tested in the transition regime has then been simulated, by three dimensional finite element method computations. Ductile tearing process preceding the cleavage onset at those temperatures regime was well reproduced by the Rousselier's model. Failure probabilities, related to given stress states, has been given by post-processor calculations, using a probabilistic model based on the specific cleavage fracture process. Fracture toughness scatter of the steel, tested in the transition regime, is then well reproduced by those calculations. However, the critical cleavage stress of an elementary volume, that scales for the fracture process, is still assumed to be temperature dependant. Numerical simulations of the local fracture process suggest that this temperature effect can partly be explained by the temperature dependant decrease of the stress amplification due to the MnS clusters. (author)

  13. A cleavage toughness master curve model

    International Nuclear Information System (INIS)

    Development of fusion power will require a fracture toughness database, derived largely from small specimen tests, closely integrated with methods to assess first wall and blanket structural integrities. A master curve-shift (MC-ΔT) method has been proposed as an engineering expedient to treat the effects of structural geometry, irradiation, loading rates and safety margins. However, a number of issues related to the MC-ΔT method remain to be resolved, including the universality of MC shapes. A new micromechanical model of fracture toughness in the cleavage transition regime is proposed that combines analytical representations of finite element analysis simulations of crack-tip stress fields with a local critical stress-critical stressed area (σ*-A*) fracture criterion. This model, has been successful in predicting geometry effects, as well as high loading rate and irradiation hardening-induced Charpy shifts. By incorporating a modest temperature dependence in σ*(T), an inconsistency between model predictions and an observed universal-type MC shape is resolved

  14. Invasive cleavage of nucleic acids

    Energy Technology Data Exchange (ETDEWEB)

    Prudent, James R. (Madison, WI); Hall, Jeff G. (Madison, WI); Lyamichev, Victor I. (Madison, WI); Brow, Mary Ann D. (Madison, WI); Dahlberg, James E. (Madison, WI)

    2002-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof.

  15. Invasive cleavage of nucleic acids

    Science.gov (United States)

    Prudent, James R.; Hall, Jeff G.; Lyamichev, Victor I.; Brow, Mary Ann D.; Dahlberg, James E.

    1999-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof.

  16. Intrinsic transcript cleavage activity of RNA polymerase.

    OpenAIRE

    Orlova, M; Newlands, J; Das, A; Goldfarb, A; Borukhov, S

    1995-01-01

    The GreA and GreB transcript cleavage factors of Escherichia coli suppress elongation arrest and may have a proofreading role in transcription. With the use of E. coli greA-greB- mutant, RNA polymerase is demonstrated to possess substantial intrinsic transcript cleavage activity. Mildly alkaline pH mimics the effect of the Gre proteins by inducing transcript cleavage in ternary complexes and antagonizing elongation arrest through a cleavage-and-restart reaction. Thus, transcript cleavage cons...

  17. Sequence-Specific Ultrasonic Cleavage of DNA

    OpenAIRE

    Grokhovsky, Sergei L.; Il'icheva, Irina A.; Nechipurenko, Dmitry Yu.; Golovkin, Michail V.; Panchenko, Larisa A.; Polozov, Robert V.; Nechipurenko, Yury D.

    2011-01-01

    We investigated the phenomenon of ultrasonic cleavage of DNA by analyzing a large set of cleavage patterns of DNA restriction fragments using polyacrylamide gel electrophoresis. The cleavage intensity of individual phosphodiester bonds was found to depend on the nucleotide sequence and the position of the bond with respect to the ends of the fragment. The relative intensities of cleavage of the central phosphodiester bond in 16 dinucleotides and 256 tetranucleotides were determined by multiva...

  18. Crack tip blunting and cleavage under dynamic conditions

    Science.gov (United States)

    Rajan, V. P.; Curtin, W. A.

    2016-05-01

    In structural materials with both brittle and ductile phases, cracks often initiate within the brittle phase and propagate dynamically towards the ductile phase. The macroscale, quasistatic toughness of the material thus depends on the outcome of this microscale, dynamic process. Indeed, dynamics has been hypothesized to suppress dislocation emission, which may explain the occurrence of brittle transgranular fracture in mild steels at low temperatures (Lin et al., 1987). Here, crack tip blunting and cleavage under dynamic conditions are explored using continuum mechanics and molecular dynamics simulations. The focus is on two questions: (1) whether dynamics can affect the energy barriers for dislocation emission and cleavage, and (2) what happens in the dynamic "overloaded" situation, in which both processes are energetically possible. In either case, dynamics may shift the balance between brittle cleavage and ductile blunting, thereby affecting the intrinsic ductility of the material. To explore these effects in simulation, a novel interatomic potential is used for which the intrinsic ductility is tunable, and a novel simulation technique is employed, termed as a "dynamic cleavage test", in which cracks can be run dynamically at a prescribed energy release rate into a material. Both theory and simulation reveal, however, that the intrinsic ductility of a material is unaffected by dynamics. The energy barrier to dislocation emission appears to be identical in quasi-static and dynamic conditions, and, in the overloaded situation, ductile crack tip behavior ultimately prevails since a single emission event can blunt and arrest the crack, preventing further cleavage. Thus, dynamics cannot embrittle a ductile material, and the origin of brittle failure in certain alloys (e.g., mild steels) appears unrelated to dynamic effects at the crack tip.

  19. Centralspindlin in Rappaport's cleavage signaling.

    Science.gov (United States)

    Mishima, Masanori

    2016-05-01

    Cleavage furrow in animal cell cytokinesis is formed by cortical constriction driven by contraction of an actomyosin network activated by Rho GTPase. Although the role of the mitotic apparatus in furrow induction has been well established, there remain discussions about the detailed molecular mechanisms of the cleavage signaling. While experiments in large echinoderm embryos highlighted the role of astral microtubules, data in smaller cells indicate the role of central spindle. Centralspindlin is a constitutive heterotetramer of MKLP1 kinesin and the non-motor CYK4 subunit and plays crucial roles in formation of the central spindle and recruitment of the downstream cytokinesis factors including ECT2, the major activator of Rho during cytokinesis, to the site of division. Recent reports have revealed a role of this centralspindlin-ECT2 pathway in furrow induction both by the central spindle and by the astral microtubules. Here, a unified view of the stimulation of cortical contractility by this pathway is discussed. Cytokinesis, the division of the whole cytoplasm, is an essential process for cell proliferation and embryonic development. In animal cells, cytokinesis is executed using a contractile network of actin filaments driven by a myosin-II motor that constricts the cell cortex (cleavage furrow ingression) into a narrow channel between the two daughter cells, which is resolved by scission (abscission) [1-3]. The anaphase-specific organization of the mitotic apparatus (MA, spindle with chromosomes plus asters) positions the cleavage furrow and plays a major role in spatial coupling between mitosis and cytokinesis [4-6]. The nucleus and chromosomes are dispensable for furrow specification [7-10], although they contribute to persistent furrowing and robust completion in some cell types [11,12]. Likewise, centrosomes are not essential for cytokinesis, but they contribute to the general fidelity of cell division [10,13-15]. Here, classical models of cleavage furrow

  20. Study of cleavage initiation under thermal shock by tests on cracked rings and thermomechanical calculations

    International Nuclear Information System (INIS)

    This article describes a new type of test that easily creates a thermal shock combined with mechanical loading by using standard laboratory equipments. The method consists of rapidly heating a ring initially at -175 deg. C by circulating hot water through judiciously placed holes. It allows to obtain, at minimal cost, data on crack initiation under thermal shock in the transition zone of steel 16MND5 used for pressure vessels, these data being necessary for work on fracture criteria. Details of two tests are given, one with preloading in which cleavage fracture was observed and one without preloading in which cleavage initiation did not occur. The thermomechanical calculations necessary for the interpretation of both tests are also given. Finally, the global approach to fracture is used involving comparison of the loading paths J(T) with the master curves [ASTM E1921-97, 1997. Standard test method for determination of reference temperature to for ferritic steels in the transition range, ASTM standards], as well as the local approach proposed by Beremin [Beremin, F.M., 1983. A local criterion for cleavage fracture of a nuclear pressure vessel steel. Metall. Trans. A 14A, 2777-2287] for estimating the probability of fracture of such rings. It is shown that, in both approaches, the calculated probabilities are consistent with the experimental observations

  1. The role of spaced cleavage on the porosity and permeability within a reservoir unit

    Energy Technology Data Exchange (ETDEWEB)

    Thorn, P.A.; Lageson, D.R. [Montana State Univ., Bozeman, MT (United States)

    1996-06-01

    Tectonic deformation plays a significant role in both the enhancement and degradation of the porosity and permeability within a reservoir unit. Enhancing mechanisms generally include fracturing and brecciation, whereas reducing mechanisms include cataclasis and pressure solution. Spaced cleavage is common within argillaceous limestone in foreland fold and thrust belts, including the Sawtooth Range, Montana. The presence of spaced cleavage will have a significant impact on both the permeability and porosity within a reservoir. Spaced cleavage is formed by pressure solution, where calcite is dissolved as a tectonic stress is applied. As the calcite is being removed, relatively insoluble minerals, predominately clay and quartz, are concentrated along the dissolution sites and form thin domains. The minerals within these domains are compacted and aligned perpendicular to the direction of maximum stress. Due to the nature of the aligned minerals, fluid flow will be restricted across these domains, creating severe reservoir anisotropy within the unit. Once the calcite has been dissolved, it must re-precipitate out. This will generally occur in the pores and open fractures present in the cleaved unit, significantly reducing the porosity present in the reservoir rock. However, if the cleavage has been folded during a later deformational event, these domains, which represent weaknesses in the rock, could open up around the crests of folds and provide a pathway for increased fluid migration parallel to the cleavage trend.

  2. An investigation of crack-tip stress field criteria of predicting cleavage-crack initiation

    International Nuclear Information System (INIS)

    Cleavage-crack initiation in large-scale wide-plate (WP) specimens could not be accurately predicted from small, compact (CT) specimens by using a linear-elastic fracture-mechanics, KIc, methodology. In the wide-plate tests conducted by the Heavy-Section Steel Technology Program at Oak Ridge National Laboratory, crack initiation has consistently occurred at stress-intensity (KI) values ranging from two to four times those predicted by the CT specimens. Studies were initiated to develop crack-tip stress field criteria incorporating effects of geometry, size, and constraint that will lead to improved predictions of cleavage initiation in WP specimens from CT specimens. The work centers around nonlinear two-and three-dimensional finite-element analyses of the crack-tip stress fields in these geometries. Analyses were conducted on CT and WP specimens for which cleavage initiation fracture had been measured in laboratory tests. The local crack-tip field generated for these specimens were then used in the evaluation of fracture correlation parameters to augment the KI parameter for predicting cleavage initiation. Parameters of hydrostatic constraint and of maximum principal stress, measured volumetrically, are included in these evaluations. The results suggest that the cleavage initiation process can be correlated with the local crack-tip fields via a maximum principal stress criterion based on achieving a critical area within a critical stress contour. This criterion has been successfully applied to correlate cleavage initiation in 2T-CT and WP specimen geometries. 23 refs., 16 figs., 5 tabs

  3. Shoulder Fractures

    Science.gov (United States)

    ... a Hand Therapist? Media Find a Hand Surgeon Shoulder Fractures Email to a friend * required fields From * ... can create difficulty with its function. Types of Shoulder Fractures The type of fracture varies by age. ...

  4. Kinetics of hairpin ribozyme cleavage in yeast.

    OpenAIRE

    Donahue, C P; Fedor, M J

    1997-01-01

    Hairpin ribozymes catalyze a self-cleavage reaction that provides a simple model for quantitative analyses of intracellular mechanisms of RNA catalysis. Decay rates of chimeric mRNAs containing self-cleaving ribozymes give a direct measure of intracellular cleavage kinetics in yeast. Intracellular ribozyme-mediated cleavage occurs at similar rates and shows similar inhibition by ribozyme mutations as ribozyme-mediated reactions in vitro, but only when ribozymes are located in a favorable mRNA...

  5. Influence of the austenitizing temperature in the cleavage facet size of Niocor 2

    International Nuclear Information System (INIS)

    Convetional Charpy specimens of Niocor 2 steel cooled in air from various austenitizing temperatures were fractured at -1960 C so as to insure failure by cleavage. The cleavage facet size distribution was determined and then correlated with the grain size and other aspects of the microstructure. The results that the average facet size can be increased through a coarsening of the microstructure. For the case where the γ→α transformation products are predominantely acicular, the facet size is shown to depend on substructural aspects primarily the lath packet size. (Author)

  6. Cleavage speed and implantation potential of early-cleavage embryos in IVF or ICSI cycles

    OpenAIRE

    Lee, Meng-Ju; Lee, Robert Kuo-Kuang; Lin, Ming-Huei; Hwu, Yuh-Ming

    2012-01-01

    We examined whether there is a correlation among early embryo cleavage, speed of cleavage, and implantation potential for in-vitro fertilization (IVF) treatment and intracytoplasmic sperm injection (ICSI). This retrospective study examined 112 cycles of IVF and 82 cycles of ICSI in patients less than 40 years of age. Early cleavage was defined as embryonic mitosis occurring 25–27 h after insemination. These day-3 embryos were then grouped according to cleavage speed (rapid, normal, and slow) ...

  7. Pre-mRNA 3’ Cleavage is Reversibly Inhibited In Vitro by Cleavage Factor Dephosphorylation

    OpenAIRE

    Ryan, Kevin

    2007-01-01

    During 3' end formation most pre-mRNAs undergo endonucleolytic cleavage and polyadenylation in the 3' untranslated region. Very little is known concerning the role that post-translational modifications play in the function and regulation of the factors required for 3' cleavage. Using the reconstituted pre-mRNA cleavage reaction, we find that non-specific dephosphorylation of HeLa cell nuclear extract leads to the loss of 3' cleavage activity. A variety of serine/threonine phosphatases inhibit...

  8. Cleavage crack propagation and arrest in a nuclear pressure vessel steel

    International Nuclear Information System (INIS)

    The integrity assessment of Reactor Pressure Vessels, mainly based on crack initiation, can be completed by studying crack propagation and arrest. Whereas engineering approaches do not take into account dynamic effects, these effects are important in unstable cleavage crack propagation, arrest and possible propagation re-initiation events. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture in the framework of local approach to fracture. Experiments were carried out on thin CT 25 specimens made of 16MND5 PWR vessel steel at five temperatures (-150 degrees C, -125 degrees C, -100 degrees C, -75 degrees C, -50 degrees C). Two kinds of crack path, straight or branching path, were observed. Branching cracks appear for the highest critical loadings at initiation, that increase the elastic stored energy and the effect of plasticity. The elastic-viscoplastic behavior of the ferritic steel was studied up to a strain rate of 104 s-1 and taken into account in the numerical simulations. The extended Finite Element Method (X-FEM) was used in CAST3M FE software to model crack propagation. Numerical computations combine a local non linear dynamic approach with a RKR type fracture stress criterion. The different physical micro-mechanisms, involved in cleavage fracture, were examined by the means of SEM fracture surface analyses at different temperatures and strain rates for the two kinds of crack path. The links of the critical fracture stress with both temperature and strain rate for straight crack path as well as analyses of branching crack phenomena were considered by the means of Scanning Electron Microscopy (SEM) fracture surface analyses, 3D quantitative optical microscopy and FE computations in order to aim at a robust physical justification of the propagation model which has already been developed at CEA in the frame of the B. Prabel PhD. (authors)

  9. SACRAL FRACTURES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Objective. To delineate the clinical spectrum and treatment choice of sacral fractures.Methods. In this series, 39 sacral fractures were retrospectively reviewed and classified utilizing Denis′ classification. There were 21 Zone Ⅰ fractures, 6 Zone Ⅱ fractures and 12 Zone Ⅲ fractures. Neurological deficits were present in seven patients. Thirty seven patients were treated conservatively and two underwent surgical management.Results.Thirty eight patients were followed up for three months to 19 years. Thirty three have recovered, four improved, and one remained disabled.Conclusion.The treatment of sacral fractures requires assessment of pelvic stability and existing nerve injury. The patients with pelvic ring instability and neurological deficits should be treated with fracture reduction and stability reconstruction. When the patients with pelvic fracture are complicated with neurological deficits, sacral fracture should be first suspected. Once the diagnosis of sacral fracture is made, fracture reduction should be indicated. Conservative treatment usually permits satisfactory results.

  10. Fracture toughness studies in sintered SmCo5 magnets

    International Nuclear Information System (INIS)

    The fracture toughness of sintered SmCo5 magnets were systematically evaluated using both three point bend tests as well as Vickers indentation tests. These results were used for establishing the empirical dimensionless constant (χ) for evaluating indentation fracture toughness in SmCo5 magnets. The anisotropic behaviour of mechanical properties such as hardness, elastic modulus and fracture toughness was also investigated. - Highlights: • A strong anisotropy in the elastic modulus was observed in sintered SmCo5 magnet. • The hardness and fracture toughness did not show any prominent anisotropy. • Brittle cleavage fracture with (10 0) and (10 1) type cleavage planes observed. • Fracture toughness of SmCo5 magnets using Vickers indentation technique studied. • A suitable crack model and dimensionless coefficient value determined

  11. Intergranular brittle fracture of a low alloy steel. Global and local approaches

    International Nuclear Information System (INIS)

    The intergranular brittle fracture of a low alloy steel (A533B.Cl1) is studied: an embrittlement heat treatment is used to develop two brittle 'states' that fail through an intergranular way at low temperatures. This mode of fracture leads to an important shift of the transition temperature (∼ 165 deg C) and a decrease in the fracture toughness. The local approach to fracture, developed for cleavage, is applied to the case of intergranular fracture. Modifications are proposed. The physical supports of these models are verified by biaxial (tension-torsion) tests. From the local approaches developed for intergranular fracture, the static and dynamic fracture toughness of the embrittled steel is predicted. The local approach applied to a structural steel, which presents mixed modes of fracture (cleavage and intergranular), showed that this mode of fracture seems to be controlled by intergranular loss of cohesion

  12. Delaminations by Cleavage Cracking in Duplex Stainless Steels at Sub-zero Temperatures

    Science.gov (United States)

    Pilhagen, Johan; Sandström, Rolf

    2013-10-01

    Impact toughness testing was conducted on 10 and 30 mm plates of 2205 together with a 30 mm plate of LDX 2101® duplex stainless steel (DSS). The testing temperatures were between 153 K (-120 °C) and room temperature. Interrupted fracture toughness tests of the 10 mm plate and a 50 mm plate of 2205 were also performed. The conclusion from the fractographic investigation was that the delaminations that occur in hot-rolled DSSs were cleavage fractures. The toughness anisotropy can be explained by the cleavage fracture and the appearance of the microstructure. The result from the interrupted fracture toughness test revealed that the delaminations initiated prior to the maximum force plateau and propagated ahead of the stable crack growth during testing. Estimated upper limit for the fracture delamination initiation toughness at sub-zero temperatures for the 2205 base metal according to the crack-tip opening displacement method was 28 to 61 μm for the 10 mm plate, 70 to 106 μm for the 30 mm plate and below 100 μm for the 50 mm plate.

  13. Experiments on schistosity and slaty cleavage

    Science.gov (United States)

    Becker, George Ferdinand

    1904-01-01

    Schistosity as a structure is important, and it is a part of the business of geologists to explain its origin. Slaty cleavage has further and greater importance as a possible tectonic feature. Scarcely a great mountain range exists, or has existed, along the course of which belts of slaty rock are not found, the dip of the cleavage usually approaching verticality. Are these slate belts equivalent to minutely distributed step faults of great total throw, or do they indicate compression perpendicular to the cleavage without attendant relative dislocation? Evidently the answer to this question is of first importance in the interpretation of orogenic phenomena.

  14. Rib Fractures

    Science.gov (United States)

    ... 2 Diabetes, Heart Disease a Dangerous Combo Are 'Workaholics' Prone to OCD, Anxiety? ALL NEWS > Resources First ... Rib Fractures Traumatic Pneumothorax Tension Pneumothorax Rib fractures cause severe pain, particularly when a person breathes deeply. ...

  15. Cleavage site analysis in picornaviral polyproteins

    DEFF Research Database (Denmark)

    Blom, Nikolaj; Hansen, Jan; Blaas, Dieter;

    1996-01-01

    Picornaviral proteinases are responsible for maturation cleavages of the viral polyprotein, but also catalyze the degradation of cellular targets. Using graphical visualization techniques and neural network algorithms, we have investigated the sequence specificity of the two proteinases 2Apro and 3......Cpro. The cleavage of VP0 (giving rise to VP2 and VP4), which is carried out by a so-far unknown proteinase, was also examined. In combination with a novel surface exposure prediction algorithm, our neural network approach successfully distinguishes known cleavage sites from nocleavage sites and yields...... a more consistent definition of features common to these sites. The method is able to predict experimentally determined cleavage sites in cellular proteins. We present a list of mammalian and other proteins that are predicted to be possible targets for the viral proteinases. Whether these proteins...

  16. Centrosomes: CNN's Broadcast Reaches the Cleavage Furrow

    OpenAIRE

    Sullivan, William

    2009-01-01

    Centrosomin (CNN), a core Drosophila centrosome protein, interacts with the newly identified protein Centrocortin to promote cleavage furrow formation in the early embryo. Significantly, this activity is distinct from CNN's well-established role in centrosome-based microtubule organization.

  17. Stress distribution and fracture behavior of beryllium compact tension specimens

    International Nuclear Information System (INIS)

    Compact tension specimens of beryllium (Be) were designed to study fracture behavior and mechanical properties. The local stress distribution near a notch in a compact tension specimen was measured in situ by the combination of an X-ray stress analysis and a custom-designed load device. The fracture morphology was observed by scanning electron microscopy. The result showed that the local stresses near the notch tip are much higher than in other areas, and cracking occurs first in that area. The load-crack opening displacement curve of the Be compact tension specimen was obtained, and used to calculate the fracture toughness as 15.7 MPa√m. The compact tension specimen fracture surfaces were mainly characterized by cleavage fracture over three different areas. Cleavage micro-cracks along the basal slip plane were formed at the crack tip, and their growth was controlled by the primary stress after reaching a critical length

  18. Root fractures

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Christensen, Søren Steno Ahrensburg; Tsilingaridis, Georgios

    2012-01-01

    The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed.......The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed....

  19. Bending Strength and Fracture Behavior of Ni50Mn29Ga21 Alloy with Terbium

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zeng-qi; XIONG Wei; WU Shuang-xia; WANG Xin-lin

    2004-01-01

    The bending strength and fracture behaviors of Ni50Mn29Ga21 alloy with terbium were investigated. The results show that the bending strength of the alloy is increased dramatically with the increase of terbium content. The fracture appearance of the sample without terbium is dominated by grain boundary fracture, while that with terbium is dominated by cleavage fracture with the increase of terbium content.Moreover, the grains are refined obviously and the oxygen content is decreased after adding terbium.

  20. Secondary foundry alloy damage and particle fracture

    Energy Technology Data Exchange (ETDEWEB)

    Berdin, C.; Ouglova, A.; Djafari, V.; Doglione, R

    2003-09-25

    The damage mechanisms of a hypoeutectic Al-Si-Cu foundry alloy, obtained through die casting, have been studied. Observations were made during tensile tests using a tensile test machine that was inserted into an scanning electron microscope. The microstructure features that are critical for damage were determined. The cleavage fracture of intermetallic particles was found to be the main process that limited the alloy ductility. Shrinkage cavities mainly play a role in the final fracture stage; the reduction in cross-section area induced by shrinkage cavities was assumed to be the main contribution of these defects to the fracture of the specimens. Attempts were made to determine the cleavage stress that initiated the fracture of the particles. Three-dimensional finite element computations were performed considering particular locations at the free surface of the observed fractured particles. The maximum principal stress was calculated for different locations of the particle with reference to the free surface. Different shapes and different elastic behaviour were studied. It was shown that the influence of a free surface on the stress level in a particle depends on its shape. The results were compared with those found in literature concerning the fracture strength of particles in Al alloys.

  1. Propagation and arrest of cleavage cracks in a nuclear pressure vessel steel

    International Nuclear Information System (INIS)

    The safety of nuclear structures is crucial while the service time of nuclear power stations is planned to be extended up to 60 years. Initiation stage of cracks is still considered as a key issue, but more and more component integrity analyses investigate the crack arrest possibility. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture. Experiments using standard measuring techniques and a high-speed framing camera system, as well as Scanning Electron Microscope fracture surface analyses were carried out on thin CT specimens made of 16MND5 PWR vessel steel. The elastic-viscoplastic behavior of the ferritic steel has been studied and taken into account in numerical simulations. The extended Finite Element Method (X-FEM) is used in CAST3M finite element analysis software to model crack propagation. Numerical computations combine a local non-linear dynamic approach and a fracture criterion based on critical cleavage stress, whereas current standards in the nuclear field use a global static approach to fracture to depict crack initiation and arrest. The links of the criterion with temperature and strain rate are considered thanks to experiments, SEM fractographies and 2D computations in order to get a robust physical model which can be effective for model-based predictions of industrial structures. (authors)

  2. Assessment of grain boundary segregation inducing intergranular fracture

    International Nuclear Information System (INIS)

    Intergranular fracture is often attributed to grain boundary embrittlement resulting from the segregation of some embrittling elements. Consequently, it is often associated with catastrophic premature brittle fracture, in particular with respect to the more common transgranular cleavage fracture. One of the embrittling elements known to promote intergranular fracture of reactor pressure vessel steels under irradiation is phosphorus, even without hardening. To better assess the effect of intergranular grain boundary segregation on the mechanical properties of reactor pressure vessel steels, an experimental program was carried out on an embrittled steel through a step cooling heat treatment. This reversible temper embrittlement treatment consists of gradually cooling the steel in the range 600-400 deg. C with increasing time resulting in phosphorus segregation to grain boundaries. Tensile, Charpy impact and fracture toughness tests were performed in both as received and step cooled condition, together with scanning electron microscopy examination to reveal the fracture mode. The results show that intergranular fracture is not as catastrophic as originally thought. Crack instability is clearly higher during transgranular cleavage than intergranular fracture. The interpretation of experimental results based on the Charpy impact test can be biased by the ductile fracture contribution. Experimental data including both Charpy impact and fracture toughness could be analyzed in a consistent way allowing for an improved interpretation. (authors)

  3. Does Cleavage Work at Work? Men, but Not Women, Falsely Believe Cleavage Sells a Weak Product

    Science.gov (United States)

    Glick, Peter; Chrislock, Karyna; Petersik, Korinne; Vijay, Madhuri; Turek, Aleksandra

    2008-01-01

    We examined whether men, but not women, would be distracted by a female sales representative's exposed cleavage, leading to greater perceived efficacy for a weak, but not for a strong product. A community sample of 88 men and 97 women viewed a video of a female pharmaceutical sales representative who (a) had exposed cleavage or dressed modestly…

  4. Selective cleavage of pepsin by molybdenum metallopeptidase

    Energy Technology Data Exchange (ETDEWEB)

    Yenjai, Sudarat; Malaikaew, Pinpinat; Liwporncharoenvong, Teerayuth [Department of Chemistry, Faculty of Science, Srinakharinwirot University, Sukhumvit 23, Bangkok 10110 (Thailand); Buranaprapuk, Apinya, E-mail: apinyac@swu.ac.th [Department of Chemistry, Faculty of Science, Srinakharinwirot University, Sukhumvit 23, Bangkok 10110 (Thailand)

    2012-03-02

    Graphical abstract: Molybdenum metallopeptidase: the Mo(VI) cluster with six molybdenum cations has the ability to cleave protein under mild conditions (37 Degree-Sign C, pH 7) without reducing agents. The reaction required only low concentration of ammonium heptamolybdatetetrahydrate ((NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}{center_dot}4H{sub 2}O) (0.125 mM). The reaction undergoes possibly via a hydrolytic mechanism. This is the first demonstration of protein cleavage by a molybdenum cluster. Highlights: Black-Right-Pointing-Pointer This is the first demonstration of protein cleavage by a Mo(VI) cluster with six molybdenum cations. Black-Right-Pointing-Pointer The cleavage reaction undergoes at mild conditions. Black-Right-Pointing-Pointer No need of reducing agents. Black-Right-Pointing-Pointer Only low concentration of Mo(VI) cluster and short time of incubation are needed. -- Abstract: In this study, the cleavage of protein by molybdenum cluster is reported for the first time. The protein target used is porcine pepsin. The data presented in this study show that pepsin is cleaved to at least three fragments with molecular weights of {approx}23, {approx}19 and {approx}16 kDa when the mixture of the protein and ammonium heptamolybdate tetrahydrate ((NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}{center_dot}4H{sub 2}O) was incubated at 37 Degree-Sign C for 24 h. No self cleavage of pepsin occurs at 37 Degree-Sign C, 24 h indicating that the reaction is mediated by the metal ions. N-terminal sequencing of the peptide fragments indicated three cleavage sites of pepsin between Leu 112-Tyr 113, Leu 166-Leu 167 and Leu 178-Asn 179. The cleavage reaction occurs after incubation of the mixture of pepsin and (NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}{center_dot}4H{sub 2}O) only for 2 h. However, the specificity of the cleavage decreases when incubation time is longer than 48 h. The mechanism for cleavage of pepsin is expected to be hydrolytic chemistry of the amide bonds in the protein

  5. Selective cleavage of pepsin by molybdenum metallopeptidase

    International Nuclear Information System (INIS)

    Graphical abstract: Molybdenum metallopeptidase: the Mo(VI) cluster with six molybdenum cations has the ability to cleave protein under mild conditions (37 °C, pH 7) without reducing agents. The reaction required only low concentration of ammonium heptamolybdatetetrahydrate ((NH4)6Mo7O24·4H2O) (0.125 mM). The reaction undergoes possibly via a hydrolytic mechanism. This is the first demonstration of protein cleavage by a molybdenum cluster. Highlights: ► This is the first demonstration of protein cleavage by a Mo(VI) cluster with six molybdenum cations. ► The cleavage reaction undergoes at mild conditions. ► No need of reducing agents. ► Only low concentration of Mo(VI) cluster and short time of incubation are needed. -- Abstract: In this study, the cleavage of protein by molybdenum cluster is reported for the first time. The protein target used is porcine pepsin. The data presented in this study show that pepsin is cleaved to at least three fragments with molecular weights of ∼23, ∼19 and ∼16 kDa when the mixture of the protein and ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24·4H2O) was incubated at 37 °C for 24 h. No self cleavage of pepsin occurs at 37 °C, 24 h indicating that the reaction is mediated by the metal ions. N-terminal sequencing of the peptide fragments indicated three cleavage sites of pepsin between Leu 112-Tyr 113, Leu 166-Leu 167 and Leu 178-Asn 179. The cleavage reaction occurs after incubation of the mixture of pepsin and (NH4)6Mo7O24·4H2O) only for 2 h. However, the specificity of the cleavage decreases when incubation time is longer than 48 h. The mechanism for cleavage of pepsin is expected to be hydrolytic chemistry of the amide bonds in the protein backbone.

  6. Hip fracture - discharge

    Science.gov (United States)

    Inter-trochanteric fracture repair - discharge; Subtrochanteric fracture repair - discharge; Femoral neck fracture repair - discharge; Trochanteric fracture repair - discharge; Hip pinning surgery - discharge

  7. Cleavage strain in the Variscan fold belt, County Cork, Ireland, estimated from stretched arsenopyrite rosettes

    Science.gov (United States)

    Ford, M.; Ferguson, C.C.

    1985-01-01

    In south-west Ireland, hydrothermally formed arsenopyrite crystals in a Devonian mudstone have responded to Variscan deformation by brittle extension fracture and fragment separation. The interfragment gaps and terminal extension zones of each crystal are infilled with fibrous quartz. Stretches within the cleavage plane have been calculated by the various methods available, most of which can be modified to incorporate terminal extension zones. The Strain Reversal Method is the most accurate currently available but still gives a minimum estimate of the overall strain. The more direct Hossain method, which gives only slightly lower estimates with this data, is more practical for field use. A strain ellipse can be estimated from each crystal rosette composed of three laths (assuming the original interlimb angles were all 60??) and, because actual rather than relative stretches are estimated, this provides a lower bound to the area increase in the plane of cleavage. Based on the average of our calculated strain ellipses this area increase is at least 114% and implies an average shortening across the cleavage of at least 53%. However, several lines of evidence suggest that the cleavage deformation was more intense and more oblate than that calculated, and we argue that a 300% area increase in the cleavage plane and 75% shortening across the cleavage are more realistic estimates of the true strain. Furthermore, the along-strike elongation indicated is at least 80%, which may be regionally significant. Estimates of orogenic contraction derived from balanced section construction should therefore take into account the possibility of a substantial strike elongation, and tectonic models that can accommodate such elongations need to be developed. ?? 1985.

  8. Multi scale study of the plasticity at low temperature in α-iron: application for the cleavage

    International Nuclear Information System (INIS)

    An accident inside a nuclear power plant may lead to the cleavage of the nuclear vessel made of bainitic steel. In order to understand the origin of this fracture, we studied BCC-iron plasticity at low temperature using numerical simulations at different scales. Molecular Dynamics simulations show the high dependency of screw dislocation motion with temperature and stress. Results from these simulations were added to experiment data to develop a new Dislocation Dynamics code dedicated to BCC iron at low temperature. The code was used to model plasticity into a ferritic lath for various temperatures. This work confirms that cleavage is favoured by low temperatures. (author)

  9. Eurosceptism: the Birth of a New Cleavage?

    Directory of Open Access Journals (Sweden)

    Lorenzo Viviani

    2010-05-01

    Full Text Available Euroscepticism is an ambivalent and polysemic concept, consisting of the theme of the European identity, the construction of European Union as new polity, the development of an opposition as expression of new social cleavage, and finally the perspective of an ideological politicization of the european integration by national and supranational political actors. The article attempts to make light on the nature and on the dynamics of development of the euroscepticism through a sequence of analysis that starts from the identity of Europe (what we mean by euroscepticism, then addresses the social dimension of Europe (what we mean by the new european cleavage, and it finally examines the political dimension (the risks and opportunities of politicization by political parties of the european cleavage.

  10. Site-specific fracture plane determination using the FIB/TEM

    International Nuclear Information System (INIS)

    A new method for the determination of the crystallographic indices of planar fracture surfaces is described. The key innovation is the use of a focused ion beam instrument to extract two transmission electron microscopy (TEM) foils from the fracture surface. Selected area diffraction of these foils in the TEM allows the determination of the fracture plane from the cross product of two crystallographic line directions contained within the plane. This allows the indices to be determined from relatively small fracture surfaces, affording fracture plane determinations from facets on polycrystalline samples. The validation of this method using cleavage fracture in pure zinc is described

  11. Segond Fractures

    OpenAIRE

    Arneja, Shalinder S.; Furey, Matthew J.; Alvarez, Christine M.; Reilly, Christopher W.

    2010-01-01

    Initially described following cadaveric studies in the late 19th century by Dr. Paul Segond, the Segond fracture is now widely accepted as a pathognemonic radiographic marker of anterior cruciate ligament injury. This fracture in a skeletally immature 16-year-old was not seen with an anterior cruciate ligament injury, but with a Salter-Harris type IV fracture of the tibial plateau. A nonweightbearing knee immobilizer with the leg in full extension was used for 6 weeks. Recovery was uncomplica...

  12. Cleavage of cytoplasm within the oligonucleate zoosporangia of allomyces macrogynus.

    Science.gov (United States)

    Ji, Yunjeong; Song, Youngsun; Kim, Namhun; Youn, Hyunjoo; Kang, Minkook; Song, Yurim; Cho, Chungwon

    2014-01-01

    Allomyces macrogynus produces zoosporangia that discharge uninucleate zoospores after cleavage of multinucleate cytoplasm. Cleavage of cytoplasm within the oligonucleate zoosporangia of A. macrogynus was visualized by constructing three-dimensional models based on electron micrographs and confocal images. In oligonucleate zoosporangia, three adjacent nuclei can form three cleavage planes with a line of intersection of the planes. The position and boundary of the cleavage planes are thought to be determined by the relative positions of the nuclei. The establishment of three cleavage planes by cleavage membranes occurred sequentially, and the nuclear axis connecting the centers of two nuclei affected the development of cleavage membranes on each cleavage plane. In multinucleate zoosporangia, groups of three neighboring nuclei near the cell cortex may initiate the sequential establishment of cleavage planes and then may interact with the nuclei further from the cortex until the interactions of nuclei are propagated to the central region of the cytoplasm. PMID:24871589

  13. Microscopic characteristics of different fracture modes of brittle rock

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode Ⅰ , Mode Ⅱ and mixed mode Ⅰ - Ⅱ fracture, respectively . Microscopic characteristics of the three fracture modes of brittle rock were studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of Mode Ⅰ fracture has a great number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of Mode Ⅱ fracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress.The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed mode Ⅰ - Ⅱ fracture. The measured Mode Ⅱ fracture toughness K Ⅱ c and mixed mode Ⅰ -Ⅱ fracture toughness Kmc are larger than Mode Ⅰ fracture toughness KⅠc. KⅡc is about 3.5times KI c, and KmC is about 1.2 times K Ⅰ c.

  14. Prediction of proprotein convertase cleavage sites

    DEFF Research Database (Denmark)

    Duckert, Peter; Brunak, Søren; Blom, Nikolaj

    2004-01-01

    has created additional focus on proprotein processing. We have developed a method for prediction of cleavage sites for PCs based on artificial neural networks. Two different types of neural networks have been constructed: a furin-specific network based on experimental results derived from the...

  15. Cleavage site analysis in picornaviral polyproteins

    DEFF Research Database (Denmark)

    Blom, Nikolaj; Hansen, Jan; Blaas, Dieter; Brunak, Søren

    1996-01-01

    are indeed cleaved awaits experimental verification. Additionally, we report several errors detected in the protein databases. A computer server for prediction of cleavage sites by picornaviral proteinases is publicly available at the e-mail address NetPicoRNA@cbs.dtu.dk or via WWW at http://www.cbs.dtu.dk/services/NetPicoRNA...

  16. Reductive cleavage of the peptide bond

    Science.gov (United States)

    Holian, J.; Garrison, W. M.

    1973-01-01

    In many biological research efforts, long chain organic molecules are studied by breaking large molecules into smaller components. Cleavage technique of recent interest is the use of solvated electrons. These are formed when aqueous solutions are bombarded with gamma radiation. Solvated electron is very reactive and can reduce most any species present, even to form free radicals.

  17. Can laccases catalyze bond cleavage in lignin?

    DEFF Research Database (Denmark)

    Munk, Line; Sitarz, Anna Katarzyna; Kalyani, Dayanand;

    2015-01-01

    these enzymes may help degrading lignin, using oxygen as the oxidant. Laccases can catalyze polymerization of lignin, but the question is whether and how laccases can directly catalyze modification of lignin via catalytic bond cleavage. Via a thorough review of the available literature and detailed...

  18. Fracture Mechanics

    CERN Document Server

    Zehnder, Alan T

    2012-01-01

    Fracture mechanics is a vast and growing field. This book develops the basic elements needed for both fracture research and engineering practice. The emphasis is on continuum mechanics models for energy flows and crack-tip stress- and deformation fields in elastic and elastic-plastic materials. In addition to a brief discussion of computational fracture methods, the text includes practical sections on fracture criteria, fracture toughness testing, and methods for measuring stress intensity factors and energy release rates. Class-tested at Cornell, this book is designed for students, researchers and practitioners interested in understanding and contributing to a diverse and vital field of knowledge. Alan Zehnder joined the faculty at Cornell University in 1988. Since then he has served in a number of leadership roles including Chair of the Department of Theoretical and Applied Mechanics, and Director of the Sibley School of Mechanical and Aerospace Engineering.  He teaches applied mechanics and his research t...

  19. Cross talk between the +73/294 interaction and the cleavage site in RNase P RNA mediated cleavage

    OpenAIRE

    Brännvall, Mathias; Kikovska, Ema; Kirsebom, Leif A.

    2004-01-01

    To monitor functionally important metal ions and possible cross talk in RNase P RNA mediated cleavage we studied cleavage of substrates, where the 2′OH at the RNase P cleavage site (at −1) and/or at position +73 had been replaced with a 2′ amino group (or 2′H). Our data showed that the presence of 2′ modifications at these positions affected cleavage site recognition, ground state binding of substrate and/or rate of cleavage. Cleavage of 2′ amino substituted substrates at different pH showed ...

  20. Initiation of cleavage in a low alloy steel: effect of a ductile damage localized around inclusions; Declenchement du clivage dans un acier faiblement allie: role de l'endommagement ductile localise autour des inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Carassou, S

    2000-07-01

    The fracture mechanism in a low alloy steel, used in the pressurised water reactor vessel, has been studied in the ductile to brittle transition temperature range. We used the local approach of fracture in conjunction with both fractographic observations and numerical simulations. Previous studies suggested the onset of cleavage to be favoured by the presence of nearby manganese sulphide (MnS) clusters: the ductile damaged zone localised inside a cluster increases the stress around it, and so contribute to the triggering of cleavage due to nearby classical sites, like carbides. The experimental study of size dependence and anisotropy on the global fracture behaviour, together with fractographic observations, give here the proof of the influence of MnS clusters on the onset of cleavage in this steel. Fracture behaviour of pre-cracked specimens tested in the transition regime has then been simulated, by three dimensional finite element method computations. Ductile tearing process preceding the cleavage onset at those temperatures regime was well reproduced by the Rousselier's model. Failure probabilities, related to given stress states, has been given by post-processor calculations, using a probabilistic model based on the specific cleavage fracture process. Fracture toughness scatter of the steel, tested in the transition regime, is then well reproduced by those calculations. However, the critical cleavage stress of an elementary volume, that scales for the fracture process, is still assumed to be temperature dependant. Numerical simulations of the local fracture process suggest that this temperature effect can partly be explained by the temperature dependant decrease of the stress amplification due to the MnS clusters. (author)

  1. Autoproteolytic Cleavage and Activation of Human Acid Ceramidase*

    OpenAIRE

    Shtraizent, Nataly; Eliyahu, Efrat; Park, Jae-Ho; He, Xingxuan; Shalgi, Ruth; Schuchman, Edward H.

    2008-01-01

    Herein we report the mechanism of human acid ceramidase (AC; N-acylsphingosine deacylase) cleavage and activation. A highly purified, recombinant human AC precursor underwent self-cleavage into α and β subunits, similar to other members of the N-terminal nucleophile hydrolase superfamily. This reaction proceeded with first order kinetics, characteristic of self-cleavage. AC self-cleavage occurred most rapidly at acidic pH, but also at neutral pH. Site-directed mutagene...

  2. Stress fractures

    International Nuclear Information System (INIS)

    The diagnosis of a stress fracture should be considered in patients presented with pain after a change in activity, especially if the activity is strenuous and the pain is in the lower extremities. Since evidence of the stress fracture may not be apparent for weeks on routine radiographs, proper use of other imaging techniques will allow an earlier diagnosis. Prompt diagnosis is especially important in the femur, where displacement may occur

  3. Toddler's fracture.

    OpenAIRE

    Shravat, B P; Harrop, S N; Kane, T P

    1996-01-01

    "Toddler's fracture" can be difficult to diagnose but should be suspected whenever a child presents to the accident and emergency department with a limp or fails to bear weight on the leg. Irritable hip and subacute osteomyelitis must feature in the differential diagnosis. The history may or may not include an obvious traumatic episode. Rather than fracture, elastic bowing of the bone and consequent periosteal stripping may explain symptoms in some cases.

  4. Calcium waves along the cleavage furrows in cleavage-stage Xenopus embryos and its inhibition by heparin

    OpenAIRE

    1996-01-01

    Calcium signaling is known to be associated with cytokinesis; however, the detailed spatio-temporal pattern of calcium dynamics has remained unclear. We have studied changes of intracellular free calcium in cleavage-stage Xenopus embryos using fluorescent calcium indicator dyes, mainly Calcium Green-1. Cleavage formation was followed by calcium transients that localized to cleavage furrows and propagated along the furrows as calcium waves. The calcium transients at the cleavage furrows were o...

  5. ''Global and local approaches of fracture in the ductile to brittle regime of a low alloy steel''

    International Nuclear Information System (INIS)

    The study is a contribution to the prediction of flow fracture toughness of low alloy steel and to a better knowledge of fracture behavior in the ductile to brittle transition region. Experiments were performed on a nozzle cut-off from a pressurized water reactor vessel made of steels A508C13 type steel. Axisymmetrical notched specimens were tested to study the fracture onset in a volume element while pre-cracked specimens were used to investigate cleavage fracture after stable crack growth. Systematic observations of fracture surfaces showed manganese sulfide inclusions (MnS) at cleavage sites or in the vicinity. The experimental results were used for modelling by the local approach to fracture. In a volume element the fracture is described by an original probabilistic model. This model is based on volume fraction distributions of MnS inclusions gathered in clusters and on the assumption of a competition without interaction between ductile and cleavage fracture modes. This model was applied to pre-cracked specimens (CT specimens). It is able to describe the scatter in the toughness after a small stable crack growth if a temperature effect on the cleavage stress is assumed. So, the modelling is able to give a lower bound of fracture toughness as a function of temperature. (author)

  6. Modelling with the X-FEM the dynamic propagation and arrest of a cleavage crack in PWR ferritic steel

    International Nuclear Information System (INIS)

    This PhD thesis is a study of dynamic cleavage crack propagation and arrest in a PWR steel. It is first recalled that a good understanding of phenomena involved in dynamic fracture mechanics implies good experimental data as well as an efficient numerical tool. The extended Finite Element Method is implanted in the French software Cast3M. It enables to simulate crack growth without any re-meshing. Two techniques are proposed: the level set functions update on an auxiliary grid, and the non-conforming partitioning integration to avoid fields projection in plasticity case. Experimental fracture tests are performed on three configurations: CT specimen, ring under compression in both mode I and mixed mode. Crack speed is measured. Fractography assign cleavage as responsible of fracture. A propagation model based on the principal stress evaluated at the crack tip is identified. Critical cleavage stress is found to depend on rate of phenomena. This model permits to predict accurately by numerical simulation, the crack behavior which is observed experimentally. (author)

  7. The effect of specimen and flaw dimensions on fracture toughness

    International Nuclear Information System (INIS)

    The effect of the specimen size and geometry on fracture toughness has been investigated both by experimental tests and computational analyses. The methods for constraint description, namely T-stress, Q-parameter and Small-Scale Yielding Correction (SSYC) have been compared and applied for various geometries. A statistical treatment for the specimen thickness effect on cleavage fracture toughness has been investigated. Elliptical surface cracks were compared with straight-thickness cracks and a method for crack shape correction was presented. Based on the results, the differences in apparent fracture toughness values obtained from various specimen configurations can be better understood and taken into account

  8. Regioselectivity in the Reductive Bond Cleavage of Diarylalkylsulfonium Salts

    DEFF Research Database (Denmark)

    Kampmeier, Jack; Mansurul Hoque, AKM; D. Saeva, Franklin;

    2009-01-01

    This investigation was stimulated by reports that one-electron reductions of monoaryldialkylsulfonium salts never give aryl bond cleavage whereas reductions of diarylmonoalkylsulfonium salts preferentially give aryl bond cleavage. We studied the product ratios from the reductive cleavage of di-4......- tolylethylsulfonium and di-4-tolyl-2-phenylethylsulfonium salts by a variety of one-electron reducing agents ranging in potential from -0.77 to +2.5 eV (vs SCE) and including thermal reductants, indirect electrolyses mediated by a series of cyanoaromatics, and excited singlet states. We report that the cleavage...... products vary from regiospecific alkyl cleavage to predominant aryl cleavage as a function of the potential of the reducing agent. We conclude that differences between the reductive cleavages of mono- and diarylsulfonium salts are direct consequences of the structures of the sulfuranyl radical...

  9. Distance of cleavage trigger point (weakest-link) to the crack tip - fractographic analysis

    International Nuclear Information System (INIS)

    Among the existing approaches approaches to predict Jc, in the transition region of the ferritic steels, there are statistical and deterministic methods. Among the formers we have the methodology based on the two-parameter J-Q theory and the weakest-link concept with its characteristic distance, rwl. For this work, an experimental program was developed using 65 fracture mechanics specimens made from an A508 steel, in three geometries with thickness B c, all specimen fracture surfaces were observed by scanning electron microscopy to identify the cleavage trigger points (weak-links) and to measure their characteristic distances rwl to the crap tip. The Jc and rwl values were presented and compared with the theoretical ones. (author)

  10. Regulated Cleavage of Prothrombin by Prothrombinase: REPOSITIONING A CLEAVAGE SITE REVEALS THE UNIQUE KINETIC BEHAVIOR OF THE ACTION OF PROTHROMBINASE ON ITS COMPOUND SUBSTRATE*♦

    OpenAIRE

    Bradford, Harlan N.; Micucci, Joseph A.; Krishnaswamy, Sriram

    2009-01-01

    Prothrombinase converts prothrombin to thrombin via cleavage at Arg320 followed by cleavage at Arg271. Exosite-dependent binding of prothrombin to prothrombinase facilitates active site docking by Arg320 and initial cleavage at this site. Precise positioning of the Arg320 site for cleavage is implied by essentially normal cleavage at Arg320 in recombinant prothrombin variants...

  11. Experimental study and local approach of cleavage crack arrest in a bainitic steel

    International Nuclear Information System (INIS)

    EDF wants to complete the assessment of reactor pressure vessels, usually based on crack initiation concept, by crack arrest concept. The work aims at improving the knowledge of cleavage crack arrest in a reactor pressure vessel steel. For that purpose, isothermal crack arrest experiments were performed for temperatures ranging from - 150 C up to - 50 C on compact tensile specimens and on pre-cracked rings submitted to compressive loading. Fractographic observations revealed that the whole crack propagation and arrest occurs by cleavage even if ductile tearing occurs before initiation of the unstable crack propagation. A local cleavage crack arrest criterion is applied in finite element computations carried out in elasto-visco-plasticity and in full dynamics: the crack propagates since the largest principal stress reaches a critical stress. The application of this criterion on the experiments leads to a good prediction of the crack speed and of the crack length and shows that the critical stress increases with the temperature in relation with dissipation features observed on the fracture surfaces. Dependence to the geometry is observed; it can be due to the assumption used for the 2D computations. The study of the structural dynamic shows that the crack arrest phenomenon is very linked to the global dynamics of the structure: crack arrest and crack closure occur approximately at the same time. (author)

  12. Fracture source

    Directory of Open Access Journals (Sweden)

    2003-07-01

    Full Text Available The fracture properties of many different types of fibers are covered in a timely new book that will prove to be a tremendous source of information and references for researchers in the wide and diverse field of fibers and composites, says Bill Clegg.

  13. Study of the competition between ductile tearing and brittle fracture : Application to the mechanical strength of C-Mn pipes and their welded joints.

    OpenAIRE

    Le Corre, Vincent

    2006-01-01

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture per cleavage does not exist on a cracked structure.The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition rang...

  14. Prediction of fracture in the transition regime: application to an A533B pressure vessel steel

    International Nuclear Information System (INIS)

    In order to model the fracture behaviour of pressure vessel steels in the transition regime, a new model has been developped in 1991 at EDF R and D Division in the framework of local approach to fracture. This approach couples the damage mechanics model developped by Rousselier which is accounting for ductile propagation of a crack, and the Beremin's model based on Weibull's statistics which stands for cleavage. It is possible to predict, by this coupled approach, safe lower bound transition curves for a temperature range up to RTNDT+50 C. It has been shown that the predictions of the model agree well with the experimental data, both in terms of fracture toughness at cleavage instability and the amount of pre-cleavage tearing. Those predicted curves have also been compared to the ASME design curve, and substantial safety margins have been exhibited. (orig.)

  15. A Historical Trend of Ethnic Cleavages in Contemporary Iran

    Directory of Open Access Journals (Sweden)

    Hussein Mohammadzadeh

    2013-10-01

    Full Text Available The goal of this study is evaluation social and historical content of social cleavage in contemporary Iran. Analytical framework rooted in Rokan theory. Rokan believed that social cleavage appearance post of revolutions. Method of study was historical comparatives.The method of this research is comparative historical in which we used of historical documents and data. In this field, I have compared data of indexes of socio-economic of ethnic states.Assessment of data and documents show that social cleavages and particularly ethnic cleavages rise after Reza shah revolution. He established centralized and dictated government and divided society of Iran and institutionalization the inequality in social structure. Sense of deprivation about inequality and suited circumstance activated ethnic cleavage in Iran. Decrease of inequality and justice could decrease of social deprivation and deactivated social cleavages.

  16. SVM-based prediction of caspase substrate cleavage sites

    OpenAIRE

    Wee, Lawrence JK; Tan, Tin Wee; Ranganathan, Shoba

    2006-01-01

    Background Caspases belong to a class of cysteine proteases which function as critical effectors in apoptosis and inflammation by cleaving substrates immediately after unique sites. Prediction of such cleavage sites will complement structural and functional studies on substrates cleavage as well as discovery of new substrates. Recently, different computational methods have been developed to predict the cleavage sites of caspase substrates with varying degrees of success. As the support vector...

  17. Modeling and Inferring Cleavage Patterns in Proliferating Epithelia

    OpenAIRE

    Patel, Ankit B.; Gibson, William T.; Gibson, Matthew C; Radhika Nagpal

    2009-01-01

    The regulation of cleavage plane orientation is one of the key mechanisms driving epithelial morphogenesis. Still, many aspects of the relationship between local cleavage patterns and tissue-level properties remain poorly understood. Here we develop a topological model that simulates the dynamics of a 2D proliferating epithelium from generation to generation, enabling the exploration of a wide variety of biologically plausible cleavage patterns. We investigate a spectrum of models that incorp...

  18. Dynamic propagation and cleavage crack arrest in bainitic steel

    International Nuclear Information System (INIS)

    In complement of the studies of harmfulness of defects, generally realized in term of initiation, the concept of crack arrest could be used as complementary analyses to the studies of safety. The stop occurs when the stress intensity factor becomes lower than crack arrest toughness (KIa) calculated in elasto-statics (KI ≤ KIa). The aim of this thesis is to understand and predict the stop of a crack propagating at high speed in a 18MND5 steel used in the pressure water reactor (PWR). The test chosen to study crack arrest is the disc thermal shock test. The observations under the scanning electron microscope of the fracture surface showed that the crack arrest always occurs in cleavage mode and that the critical microstructural entity with respect to the propagation and crack arrest corresponds to at least the size of the prior austenitic grain. The numerical analyses in elasto-statics confirm the conservatism of the codified curve of the RCC-M with respect to the values of KIa. The dynamic numerical analyses show that the deceleration of the crack measured at the end of the propagation is related to the global dynamic of the structure (vibrations). The transferability to components of crack arrest toughness obtained from tests analysed in static is thus not assured. The disc thermal shock tests were also modelled by considering a criterion of propagation and arrest of the type 'RKR' characterized by a critical stress sc which depends on the temperature. The results obtained account well for the crack jump measured in experiments as well as the shape of the crack arrest front. (author)

  19. Analysis of the cleavage site of the human immunodeficiency virus type 1 glycoprotein: requirement of precursor cleavage for glycoprotein incorporation.

    OpenAIRE

    Dubay, J W; Dubay, S R; Shin, H. J.; Hunter, E

    1995-01-01

    Endoproteolytic cleavage of the glycoprotein precursor to the mature SU and TM proteins is an essential step in the maturation of retroviral glycoproteins. Cleavage of the precursor polyprotein occurs at a conserved, basic tetrapeptide sequence and is carried out by a cellular protease. The glycoprotein of the human immunodeficiency virus type 1 contains two potential cleavage sequences immediately preceding the N terminus of the TM protein. To determine the functional significance of these t...

  20. Fracture mechanics

    International Nuclear Information System (INIS)

    This book entitle ''Fracture Mechanics'', the first one of the monograph ''Materiologie'' is geared to design engineers, material engineers, non destructive inspectors and safety experts. This book covers fracture mechanics in isotropic homogeneous continuum. Only the monotonic static loading is considered. This book intended to be a reference with the current state of the art gives the fundamental of the issues under concern and avoids the developments too complicated or not yet mastered for not making reading cumbersome. The subject matter is organized as going from an easy to a more complicated level and thus follows the chronological evolution in the field. Similarly the microscopic scale is considered before the macroscopic scale, the physical understanding of phenomena linked to the experimental observation of the material preceded the understanding of the macroscopic behaviour of structures. In this latter field the relatively recent contribution of finite element computations with some analogy with the experimental observation is determining. However more sensitive analysis is not skipped

  1. Fracture of laminated and in situ niobium silicide-niobium composites

    International Nuclear Information System (INIS)

    The mechanisms contributing to the fracture resistance of refractory metal intermetallic composites containing a BCC metallic phase (niobium) were investigated using model Nb-Si laminates and in situ composites. The controlling influence of ductile phase yield strength and fracture behavior were investigated by varying laminate processing parameters, and/or altering temperatures and applied strain rates during fracture experiments on all materials. The fracture behavior of ductile constituents were found to be influenced by phase grain size, solid solution content, constraint (as influenced by interfacial bond strengths), and the testing condition (high strain rates and low temperatures). The measured fracture resistance, when compared to theoretical models, was shown to be controlled by the toughness of the ductile phase and independent of the fracture behavior promoted (cleavage and ductile). The loss in ductility due to cleavage by high constraint, high strain rates and/or low temperatures was compensated by high yield and cleavage fracture stresses in order to provide a level of toughening similar to that contributed by ligaments which failed with lower yield stresses and greater strains

  2. Critical level of intergranular fracture to affect the toughness of embrittled 2.25Cr-1Mo steels

    Science.gov (United States)

    Islam, M. A.; Knott, J. F.; Bowen, P.

    2004-10-01

    In general, the low-temperature brittle fracture mode of unembrittled ferritic steel is transgranular cleavage. During temper embrittlement, impurity elements, such as sulfur (S), phosphorus (P), antimony (Sb), arsenic (As), and tin (Sn), segregate to prior austenite grain boundaries, which results in a decrease in the grain boundary cohesive strength. As a result, the brittle transgranular cleavage fracture mode changes to intergranular decohesion in association with the decrease in the critical fracture (stress (σ F) as well as the fracture toughness (K). However, the appearance of intergranular facets on the fracture surface does not cause a decrease in the K and σ F values. In this work, quenched and fully tempered 2.25Cr-1Mo steel (in an unembrittled condition that exhibits almost 100% brittle transgranular cleavage fracture) has been embrittled for 24, 96, and 210 h at 520 °C to produce different proportions of intergranular fracture. These unembrittled and embrittled steel specimens were tested to measure K (at -120 and -196 °C) and σ F (at -196 °C). The experimental results and detailed fractographic observations show that the K and σ F values decrease with an increase in the area fraction of intergranular fracture, provided that the area fraction of the intergranular facet on the brittle fracture surface exceeded a certain critical level, approximately 20 22%.

  3. Presence of Meiotic Spindles Indicates Early Cleavage of Embryos

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Objective To assess whether the detection of the meiotic spindle could anticipate the appearance of early cleavage.Methods Oocytes were obtained from stimulated ovaries of consenting patients undergoing oocytes retrieval for ICSI.Spindles were imaged with the Polscope.After ICSI,oocytes with or without spindles were cultured for examination of early cleavage and embryo development.A total of 328 oocytes from 50 cycles were examined with the Polscope and inseminated by ICSI.Results Spindles were imaged in 81.7% of oocytes.After ICSI,more oocytes with spindles (78.4%) fertilized normally than oocytes without spindles (53.3%)(P<0.001).At 25-27 h post ICSI.more fertilized oocytes developed from oocytes with spindles (81.9%) were detected early cleavage than those from oocytes without spindles(28.1%)(P<0.001).Significantly more embryos with early cleavage (82.2%) developed to high quality embryos at d 3 compared with the embryos without early cleavage(48.3%)(P=0.001).The value of rs related to the relationship between spindles and early cleavage was 0.420(P<0.0001).Conclusion The existing of the early cleavage may have a predictive value on the opportunity of high quality embryos and the existing of the spindle may have a predictive value in the appearance of early cleavage.

  4. Deletion Mapping of the Encephalomyocarditis Virus Primary Cleavage Site

    OpenAIRE

    Hahn, Harry; Palmenberg, Ann C.

    2001-01-01

    The cotranslational, primary self-cleavage reaction of cardiovirus polyprotein relies on a highly conserved, short segment of amino acids at the 2A-2B protein boundary. The amino terminus of the required element for encephalomyocarditis virus has now been mapped to include Tyr126 of the 2A protein, the 18th amino acid before the cleavage site.

  5. Si(111) cleavage and the (2 x 1) reconstruction process

    Science.gov (United States)

    Pearson, E. M.; Halicioglu, T.; Tiller, W. A.

    1987-01-01

    Using a computer simulation technique with a semiempirical potential, a Si crystal was cleaved along the (111) plane. The pi-bonded chain structural features of the Si(111) cleavage surface are observed and found to be a consequence of the dynamics of this cleavage process and seem not to be influenced by the final energetics.

  6. A photoinduced cleavage of DNA useful for determining T residues.

    OpenAIRE

    Simoncsits, A; Török, I

    1982-01-01

    Irradiation of 5'-[32P]-phosphate labeled DNA fragments with ultraviolet light in the presence of primary amines followed by piperidine treatment resulted in base-specific cleavage of the DNA chain at T residues, accompanied by a less intensive G reaction. This simple, T greater than G cleavage offers an alternative method for determining T residues in chemical DNA sequencing.

  7. Local approach and micromechanical modelling of fracture

    International Nuclear Information System (INIS)

    After an introduction into the phenomenae of brittle and ductile fracture of steels the lecture will present various micromechanical models covering different aspects of the failure process. Emphasis will be laid on the applicatin of those models covering in particular the Weibull cleavage stress, the Rice and Tracey void growth model, and the Gurson model as modified by Needleman and Tvergard. Whenever possible, the comparison of experimental and numerical results will be stressed. In conclusion, the future potential of micromechanical models will be sketched, e.g., application to other materials like composites or towards optimization of existing and design of new materials. (orig.)

  8. Distal radius triplane fracture

    OpenAIRE

    Parkar, AAH; Marya, S.; Auplish, S

    2014-01-01

    A triplane fracture is so named because of the three planes traversed by the fracture line. These are physeal fractures that result from injury during the final phase of maturation and cessation of growth. This fracture pattern typically involves the distal tibia. We present a rare case of a triplane fracture involving the distal radius.

  9. Cleavage factor Im (CFIm) as a regulator of alternative polyadenylation.

    Science.gov (United States)

    Hardy, Jessica G; Norbury, Chris J

    2016-08-15

    Most mammalian protein coding genes are subject to alternative cleavage and polyadenylation (APA), which can generate distinct mRNA 3'UTRs with differing regulatory potential. Although this process has been intensely studied in recent years, it remains unclear how and to what extent cleavage site selection is regulated under different physiological conditions. The cleavage factor Im (CFIm) complex is a core component of the mammalian cleavage machinery, and the observation that its depletion causes transcriptome-wide changes in cleavage site use makes it a key candidate regulator of APA. This review aims to summarize current knowledge of the CFIm complex, and explores the evidence surrounding its potential contribution to regulation of APA. PMID:27528751

  10. Criterion of cleavage crack propagation and arrest in a nuclear PWR vessel steel

    International Nuclear Information System (INIS)

    The purpose of this PhD thesis is to understand physical mechanisms of cleavage crack propagation and arrest in the 16MND5 PWR vessel steel and to propose a robust predicting model based on a brittle fracture experimental campaign of finely instrumented laboratory specimens associated with numerical computations. First, experiments were carried out on thin CT25 specimens at five temperatures (-150 C, -125 C, -100 C, -7 C, -50 C). Two kinds of crack path, straight or branching path, have been observed. To characterize crack propagation and to measure crack speed, a high-speed framing camera system was used, combined with the development of an experimental protocol which allowed to observe CT surface without icing inside the thermal chamber and on the specimen. The framing camera (520 000 fps) has allowed to have a very accurate estimation of crack speed on the complete ligament of CT (∼ 25 mm). Besides, to analyse experiments and to study the impact of viscosity on the mechanical response around the crack tip, the elastic-viscoplastic behavior of the ferritic steel has been studied up to a strain rate of 104 s-1 for the tested temperatures.The extended Finite Element Method (X-FEM) was used in CAST3M FE software to model crack propagation. Numerical computations combine a local non linear dynamic approach with a RKR type fracture stress criterion to a characteristic distance. The work carried out has confirmed the form of the criterion proposed by Prabel at -125 C, and has identified the dependencies of the criterion on temperature and strain rate. From numerical analyzes in 2D and 3D, a multi-temperature fracture stress criterion, increasing function of the strain rate, was proposed. Predictive modeling were used to confirm the identified criterion on two specimen geometries (CT and compressive ring) in mode I at different temperatures. SEM observations and 3D analyzes made with optical microscope showed that the fracture mechanism was the cleavage associated

  11. Scanning electron microscopical surface fracture investigations using replica method

    International Nuclear Information System (INIS)

    There are cases in surface fracture investigations in which one cannot use a direct micrographic surface fracture evaluation in the laboratory. The following work describes a technique enabling these evaluations indirectly via impressions. The quality of the impressions can be vastly improved when using 'lacquer matrixes' (dry-in matrixes), where the lacquer film is filled with technovite to strengthen it. This form of preparation with thin, technovite strengthened lacquer films which on the one hand, wet the fracture structures well in liquid state and on the other hand, can be removed in the solid state without too much sticking, enables evaluations to resolutions of approx.= 1 μm in the SEM investigations of the negative impressions. The characteristic microstructures for e.g. honeycombed fracture, cleavage, cyclic stress, H2 embrittlement, stress crack corrosion and hot cracking can be clearly indentified. (orig.)

  12. Use of Cleavage as an Aid in the Optical Determination of Minerals.

    Science.gov (United States)

    Ehlers, Ernest G.

    1980-01-01

    Described is the use of cleavage as an aid to microscopic determination of unknown minerals by immersion methods. Cleavages are examined in relation to fragment shapes, types of extinction, and cleavage-optical relationships. (Author/DS)

  13. Peptidase specificity from the substrate cleavage collection in the MEROPS database and a tool to measure cleavage site conservation.

    Science.gov (United States)

    Rawlings, Neil D

    2016-03-01

    One peptidase can usually be distinguished from another biochemically by its action on proteins, peptides and synthetic substrates. Since 1996, the MEROPS database (http://merops.sanger.ac.uk) has accumulated a collection of cleavages in substrates that now amounts to 66,615 cleavages. The total number of peptidases for which at least one cleavage is known is 1700 out of a total of 2457 different peptidases. This paper describes how the cleavages are obtained from the scientific literature, how they are annotated and how cleavages in peptides and proteins are cross-referenced to entries in the UniProt protein sequence database. The specificity profiles of 556 peptidases are shown for which ten or more substrate cleavages are known. However, it has been proposed that at least 40 cleavages in disparate proteins are required for specificity analysis to be meaningful, and only 163 peptidases (6.6%) fulfil this criterion. Also described are the various displays shown on the website to aid with the understanding of peptidase specificity, which are derived from the substrate cleavage collection. These displays include a logo, distribution matrix, and tables to summarize which amino acids or groups of amino acids are acceptable (or not acceptable) in each substrate binding pocket. For each protein substrate, there is a display to show how it is processed and degraded. Also described are tools on the website to help with the assessment of the physiological relevance of cleavages in a substrate. These tools rely on the hypothesis that a cleavage site that is conserved in orthologues is likely to be physiologically relevant, and alignments of substrate protein sequences are made utilizing the UniRef50 database, in which in each entry sequences are 50% or more identical. Conservation in this case means substitutions are permitted only if the amino acid is known to occupy the same substrate binding pocket from at least one other substrate cleaved by the same peptidase. PMID

  14. Dislocation model for twinning and fracture and its application to H.C.P. metals

    International Nuclear Information System (INIS)

    A dislocation model for deformation twinning and cleavage fracture is developed based on the dislocation theory of fracture and the anisotropic elasticity theory of dislocations. The extension of a Mode-I crack and a deformation twin is treated in a unified manner in terms of the surface energy, the twin boundary energy, and the applied stress state. A criterion is established for predicting twin nucleation or crack initiation and is applied to sixteen hexagonal metals

  15. Fracture toughness of a welded super duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Pilhagen, Johan, E-mail: pilhagen@kth.se [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden); Sieurin, Henrik [Scania CV AB, Södertälje (Sweden); Sandström, Rolf [Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden)

    2014-06-01

    Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture.

  16. Fracture toughness of a welded super duplex stainless steel

    International Nuclear Information System (INIS)

    Fracture toughness testing was conducted on standard single-edge notched bend bar specimens of base and weld metal. The material was the SAF 2906 super duplex stainless steel. The aim was to evaluate the susceptibility for brittle failure at sub-zero temperatures for the base and weld metal. The base metal was tested between −103 and −60 °C and was evaluated according to the crack-tip opening displacement method. The fracture event at and below −80 °C can be described as ductile until critical cleavage initiation occurs, which caused unstable failure of the specimen. The welding method used was submerged arc welding with a 7 wt% nickel filler metal. The welded specimens were post-weld heat treated (PWHT) at 1100 °C for 20 min and then quenched. Energy-dispersive X-ray spectroscopy analysis showed that during PWHT substitutional element partitioning occurred which resulted in decreased nickel content in the ferrite. The PWHT weld metal specimens were tested at −72 °C. The fracture sequence was critical cleavage fracture initiation after minor crack-tip blunting and ductile fracture

  17. Specific Cleavage of the Nucleoprotein of Fish Rhabdovirus.

    Science.gov (United States)

    Zhou, G-Z; Yi, Y-J; Chen, Z-Y; Zhang, Q-Y

    2015-11-01

    Siniperca chuatsi rhabdovirus (SCRV) is one of myriad rhabdoviruses recorded in fish. Preliminary data show that inhibition of the SCRV nucleoprotein (N) could significantly reduce the progeny virus titers in infected Epithelioma papulosum cyprinid (EPC) cells. Here, the authors propose that cleavage of the viral 47-kDa N protein is caspase-mediated based on caspase inhibition experiments, transient expression in EPC transfection, and analysis of cleavage sites. Cleavage of the SCRV N protein in culture was prevented by a pan-caspase inhibitor, z-VAD-FMK (z-Val-Ala-DL-Asp-fluoromethyl ketone). Subsequently, N was transiently expressed in EPC cells, the results of which indicated that the specific cleavage of N also occurred in the cells transfected with N-GFP plasmid. Several truncated fragments of the N gene were constructed and transiently transfected into EPC cells. Immunoblotting results indicated that D324 and D374 are the cleavage sites of N by caspases. The authors also found that z-VAD-FMK could inhibit the cytopathic effect in SCRV-infected EPC cells but not affect the production of infectious progeny, suggesting that the caspase-mediated cleavage of N protein is not required for in vitro SCRV replication. To the authors' knowledge, this is the first report on the cleavage of rhabdovirus proteins. PMID:25689989

  18. Bundled slaty cleavage in laminated argillite, north-central minnesota

    Science.gov (United States)

    Southwick, D.L.

    1987-01-01

    Exceptional bundled slaty cleavage (defined herein) has been found in drill cores of laminated, folded, weakly metamorphosed argillite at several localities in the early Proterozoic Animikie basin of north-central Minnesota. The cleavage domains are more closely spaced within the cleavage bundles than outside them, the mean tectosilicate grain size of siltstone layers, measured normal to cleavage, is less in the cleavage bundles than outside them, and the cleavage bundles are enriched in opaque phases and phyllosilicates relative to extra-bundle segments. These facts suggest that pressure solution was a major factor in bundle development. If it is assumed that opaque phases have been conserved during pressure solution, the modal differences in composition between intra-bundle and extra-bundle segments of beds provide a means for estimating bulk material shortening normal to cleavage. Argillite samples from the central part of the Animikie basin have been shortened a minimum of about 22%, as estimated by this method. These estimates are similar to the shortening values derived from other strain markers in other rock types interbedded with the argillite, and are also consistent with the regional pattern of deformation. ?? 1987.

  19. Measurement of temperature rise during Si cleavage

    International Nuclear Information System (INIS)

    A transient temperature change has been measured during the cleavage of Si(100) wafers both in air and in vacuum (5xl06 torr). A fine thermocouple(TC) (E type) formed by wires of diameter 25 μm was placed in a groove cut on the (100) surface where the crack was to occur. A tiny drop of thermal transfer compound was applied to enhance the thermal conduction between TC and sample surface. The thermocouple signal was recorded by a digital storage adaptor after an amplification of 10,000 by a special low noise amplifier. The width of the pulse appeared to be narrower in vacuum than in air. The difference is ascribed to effects of adsorption. Great care was taken to avoid spurious effects. The technique was tested by experiments on perspex and glass, where the results show reasonable agreement with those from previous work. Theoretical analysis of the measurements shows that the freshly cleaved surface can temporarily attain high temperatures, which is very significant for formation of surface structures

  20. Localized Calcium Signals along the Cleavage Furrow of the Xenopus Egg Are Not Involved in Cytokinesis

    OpenAIRE

    Noguchi, Tatsuhiko; Mabuchi, Issei

    2002-01-01

    It has been proposed that a localized calcium (Ca) signal at the growing end of the cleavage furrow triggers cleavage furrow formation in large eggs. We have examined the possible role of a Ca signal in cleavage furrow formation in the Xenopus laevis egg during the first cleavage. We were able to detect two kinds of Ca waves along the cleavage furrow. However, the Ca waves appeared after cleavage furrow formation in late stages of the first cleavage. In addition, cleavage was not affected by ...

  1. Detection of nucleic acid sequences by invader-directed cleavage

    Energy Technology Data Exchange (ETDEWEB)

    Brow, Mary Ann D. (Madison, WI); Hall, Jeff Steven Grotelueschen (Madison, WI); Lyamichev, Victor (Madison, WI); Olive, David Michael (Madison, WI); Prudent, James Robert (Madison, WI)

    1999-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The 5' nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based by charge.

  2. Detection of nucleic acid sequences by invader-directed cleavage

    Science.gov (United States)

    Brow, Mary Ann D.; Hall, Jeff Steven Grotelueschen; Lyamichev, Victor; Olive, David Michael; Prudent, James Robert

    1999-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The 5' nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based by charge.

  3. Prediction of proteasome cleavage motifs by neural networks

    DEFF Research Database (Denmark)

    Kesimir, C.; Nussbaum, A.K.; Schild, H.;

    2002-01-01

    We present a predictive method that can simulate an essential step in the antigen presentation in higher vertebrates, namely the step involving the proteasomal degradation of polypeptides into fragments which have the potential to bind to MHC Class I molecules. Proteasomal cleavage prediction...... the prediction of MHC Class I ligand boundaries more accurate: 65% of the cleavage sites and 85% of the non-cleavage sites are correctly determined. Moreover, we show that the neural networks trained on the constitutive proteasome data learns a specificity that differs from that of the networks...

  4. Size effects and strain localization in atomic-scale cleavage modeling.

    Science.gov (United States)

    Elsner, B A M; Müller, S

    2015-09-01

    In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics. PMID:26219654

  5. Effects of crack tip geometry on dislocation emission and cleavage A possible path to enhanced ductility

    CERN Document Server

    Schiøtz, J; Carlsson, A E

    1997-01-01

    We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with a sharp 60$^\\circ$ corner. The effect of the blunting is far less than would be expected from a smoothly blunted crack; the sharp corners preserve the stress concentration, reducing the effect of the blunting. However, for some material parameters blunting changes the preferred deformation mode from brittle cleavage to dislocation emission. In such materials, the absorption of preexisting dislocations by the crack tip can cause the crack tip to be locally arrested, causing a significant increase in the microscopic toughness of the crack tip. Continuum plasticity models have shown that even a moderate increase in the microscopic toughness can lead to an increase in the macroscopic fracture toughne...

  6. Size effects and strain localization in atomic-scale cleavage modeling

    International Nuclear Information System (INIS)

    In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics. (paper)

  7. An evaluation of analysis methodologies for predicting cleavage arrest of a deep crack in an RPV subjected to PTS loading conditions

    International Nuclear Information System (INIS)

    Several calculational procedures are compared for predicting cleavage arrest of a deep crack in the wall of a prototypical reactor pressure vessel (RPV) subjected to pressurized-thermal-shock (PTS) types of loading conditions. Three procedures examined in this study utilized the following models: (1) a static finite-element model (full bending); (2) a radially constrained static model; and (3) a thermoelastic dynamic finite-element model. A PTS transient loading condition was selected that produced a deep arrest of an axially-oriented initially shallow crack according to calculational results obtained from the static (full-bending) model. Results from the two static models were compared with those generated from the detailed thermoelastic dynamic finite-element analysis. The dynamic analyses modeled cleavage-crack propagation using node-release technique and an application-mode methodology based on dynamic fracture toughness curves generated from measured data. Comparisons presented here indicate that the degree to which dynamic solutions can be approximated by static models is highly dependent on several factors, including the material dynamic fracture curves and the propensity for cleavage reinitiation of the arrested crack under PTS loading conditions. Additional work is required to develop and validate a satisfactory dynamic fracture toughness model applicable to postcleavage arrest conditions in an RPV

  8. Detection of nucleic acids by multiple sequential invasive cleavages 02

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Jeff G. (Madison, WI); Lyamichev, Victor I. (Madison, WI); Mast, Andrea L. (Madison, WI); Brow, Mary Ann D. (Madison, WI)

    2002-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based on charge. The present invention also provides methods for the detection of non-target cleavage products via the formation of a complete and activated protein binding region. The invention further provides sensitive and specific methods for the detection of human cytomegalovirus nucleic acid in a sample.

  9. Detection of nucleic acids by multiple sequential invasive cleavages

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Jeff G. (Madison, WI); Lyamichev, Victor I. (Madison, WI); Mast, Andrea L. (Madison, WI); Brow, Mary Ann D. (Madison, WI)

    1999-01-01

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based on charge. The present invention also provides methods for the detection of non-target cleavage products via the formation of a complete and activated protein binding region. The invention further provides sensitive and specific methods for the detection of human cytomegalovirus nucleic acid in a sample.

  10. Implementation of a combinatorial cleavage and deprotection scheme

    DEFF Research Database (Denmark)

    Nielsen, John; Rasmussen, Palle H.

    1996-01-01

    Phthalhydrazide libraries are synthesized in solution from substituted hydrazines and phthalimides in several different library formats including single compounds, indexed sub-libraries and a full library. When carried out during solid-phase synthesis, this combinatorial cleavage and deprotection...

  11. Scanning tunneling microscopy of the cleavage surface of bismuth crystals

    International Nuclear Information System (INIS)

    The results of in situ studies of the surface structure of the cleavages of bismuth crystals by the method of scanning tunneling microscopy are presented. It is established that cleavage 'opens' the (111) surface with atomically smooth terraces of diatomic steps whose heights are equal to 0.4 nm or a multiple of this value. If the cleavage is made at room temperature, the boundaries of the terraces are usually curved and diffuse owing to the thermal motion with the activation energy of ∼700 K. The cleavage at liquid nitrogen or helium temperatures provides the formation of straight boundaries along the atomic rows on the surface. Twin interlayers of the quantized width of ∼7 nm are revealed. This width value indicates that the atomic planes on both sides of such interlayers intergrow with the interlayer planes inclined to them at a small angle

  12. Detection of nucleic acids by multiple sequential invasive cleavages

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Jeff G; Lyamichev, Victor I; Mast, Andrea L; Brow, Mary Ann D

    2012-10-16

    The present invention relates to means for the detection and characterization of nucleic acid sequences, as well as variations in nucleic acid sequences. The present invention also relates to methods for forming a nucleic acid cleavage structure on a target sequence and cleaving the nucleic acid cleavage structure in a site-specific manner. The structure-specific nuclease activity of a variety of enzymes is used to cleave the target-dependent cleavage structure, thereby indicating the presence of specific nucleic acid sequences or specific variations thereof. The present invention further relates to methods and devices for the separation of nucleic acid molecules based on charge. The present invention also provides methods for the detection of non-target cleavage products via the formation of a complete and activated protein binding region. The invention further provides sensitive and specific methods for the detection of human cytomegalovirus nucleic acid in a sample.

  13. Mechanisms for ribotoxin-induced ribosomal RNA cleavage

    Energy Technology Data Exchange (ETDEWEB)

    He, Kaiyu [Department of Microbiology and Molecular Genetics (United States); Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824 (United States); Zhou, Hui-Ren [Food Science and Human Nutrition (United States); Pestka, James J., E-mail: pestka@msu.edu [Department of Microbiology and Molecular Genetics (United States); Food Science and Human Nutrition (United States); Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824 (United States)

    2012-11-15

    The Type B trichothecene deoxynivalenol (DON), a ribotoxic mycotoxin known to contaminate cereal-based foods, induces ribosomal RNA (rRNA) cleavage in the macrophage via p38-directed activation of caspases. Here we employed the RAW 264.7 murine macrophage model to test the hypothesis that this rRNA cleavage pathway is similarly induced by other ribotoxins. Capillary electrophoresis confirmed that the antibiotic anisomycin (≥ 25 ng/ml), the macrocylic trichothecene satratoxin G (SG) (≥ 10 ng/ml) and ribosome-inactivating protein ricin (≥ 300 ng/ml) induced 18s and 28s rRNA fragmentation patterns identical to that observed for DON. Also, as found for DON, inhibition of p38, double-stranded RNA-activated kinase (PKR) and hematopoietic cell kinase (Hck) suppressed MAPK anisomycin-induced rRNA cleavage, while, in contrast, their inhibition did not affect SG- and ricin-induced rRNA fragmentation. The p53 inhibitor pifithrin-μ and pan caspase inhibitor Z-VAD-FMK suppressed rRNA cleavage induced by anisomycin, SG and ricin, indicating that these ribotoxins shared with DON a conserved downstream pathway. Activation of caspases 8, 9 and 3 concurrently with apoptosis further suggested that rRNA cleavage occurred in parallel with both extrinsic and intrinsic pathways of programmed cell death. When specific inhibitors of cathepsins L and B (lysosomal cysteine cathepsins active at cytosolic neutral pH) were tested, only the former impaired anisomycin-, SG-, ricin- and DON-induced rRNA cleavage. Taken together, the data suggest that (1) all four ribotoxins induced p53-dependent rRNA cleavage via activation of cathepsin L and caspase 3, and (2) activation of p53 by DON and anisomycin involved p38 whereas SG and ricin activated p53 by an alternative mechanism. Highlights: ► Deoxynivalenol (DON) anisomycin, satratoxin G (SG) and ricin are ribotoxins. ► Ribotoxins induce 18s and 28s rRNA cleavage in the RAW 264.7 macrophage model. ► Ribotoxins induce rRNA cleavage via

  14. Mechanisms for ribotoxin-induced ribosomal RNA cleavage

    International Nuclear Information System (INIS)

    The Type B trichothecene deoxynivalenol (DON), a ribotoxic mycotoxin known to contaminate cereal-based foods, induces ribosomal RNA (rRNA) cleavage in the macrophage via p38-directed activation of caspases. Here we employed the RAW 264.7 murine macrophage model to test the hypothesis that this rRNA cleavage pathway is similarly induced by other ribotoxins. Capillary electrophoresis confirmed that the antibiotic anisomycin (≥ 25 ng/ml), the macrocylic trichothecene satratoxin G (SG) (≥ 10 ng/ml) and ribosome-inactivating protein ricin (≥ 300 ng/ml) induced 18s and 28s rRNA fragmentation patterns identical to that observed for DON. Also, as found for DON, inhibition of p38, double-stranded RNA-activated kinase (PKR) and hematopoietic cell kinase (Hck) suppressed MAPK anisomycin-induced rRNA cleavage, while, in contrast, their inhibition did not affect SG- and ricin-induced rRNA fragmentation. The p53 inhibitor pifithrin-μ and pan caspase inhibitor Z-VAD-FMK suppressed rRNA cleavage induced by anisomycin, SG and ricin, indicating that these ribotoxins shared with DON a conserved downstream pathway. Activation of caspases 8, 9 and 3 concurrently with apoptosis further suggested that rRNA cleavage occurred in parallel with both extrinsic and intrinsic pathways of programmed cell death. When specific inhibitors of cathepsins L and B (lysosomal cysteine cathepsins active at cytosolic neutral pH) were tested, only the former impaired anisomycin-, SG-, ricin- and DON-induced rRNA cleavage. Taken together, the data suggest that (1) all four ribotoxins induced p53-dependent rRNA cleavage via activation of cathepsin L and caspase 3, and (2) activation of p53 by DON and anisomycin involved p38 whereas SG and ricin activated p53 by an alternative mechanism. Highlights: ► Deoxynivalenol (DON) anisomycin, satratoxin G (SG) and ricin are ribotoxins. ► Ribotoxins induce 18s and 28s rRNA cleavage in the RAW 264.7 macrophage model. ► Ribotoxins induce rRNA cleavage via

  15. A Historical Trend of Ethnic Cleavages in Contemporary Iran

    OpenAIRE

    Hussein Mohammadzadeh

    2013-01-01

    The goal of this study is evaluation social and historical content of social cleavage in contemporary Iran. Analytical framework rooted in Rokan theory. Rokan believed that social cleavage appearance post of revolutions. Method of study was historical comparatives.The method of this research is comparative historical in which we used of historical documents and data. In this field, I have compared data of indexes of socio-economic of ethnic states.Assessment of data and documents show that so...

  16. Microbial cleavage of organic C-S bonds

    Science.gov (United States)

    Kilbane, II, John J.

    1994-01-01

    A microbial process for selective cleavage of organic C--S bonds which may be used for reducing the sulfur content of sulfur-containing organic carbonaceous materials, Microorganisms of Rhodococcus rhodochrous and Bacillus sphaericus have been found which have the ability of selective cleavage of organic C--S bonds. Particularly preferred microorganisms are Rhodococcus rhodochrous strain ATCC 53968 and Bacillus sphaericus strain ATCC 53969 and their derivatives.

  17. Mutational analysis of the encephalomyocarditis virus primary cleavage.

    OpenAIRE

    Hahn, H.; Palmenberg, A C

    1996-01-01

    Sixteen substitution mutations of the conserved DvExNPGP sequence, implicated in cardiovirus and aphthovirus primary polyprotein cleavage, were created in encephalomyocarditis virus cDNA, expressed, and characterized for processing activity. Nearly all the mutations severely decreased the efficiency of the primary cleavage reaction during cell-free synthesis of viral precursors, indicating a stringent requirement for the natural sequence in this processing event. When representative mutations...

  18. Cleavage of a viral polyprotein by a cellular proteolytic activity.

    OpenAIRE

    Tian, Y. C.; Shih, D S

    1986-01-01

    The 200,000-dalton polyprotein encoded by the bottom component RNA of cowpea mosaic virus was synthesized in rabbit reticulocyte lysates, and this in vitro-synthesized protein was isolated from the lysate reaction mixture by sucrose density gradient centrifugation. Incubation of the isolated polyprotein with buffer caused no change in the protein, but incubation with reticulocyte lysates or with fractionated lysate proteins resulted in cleavage of the protein into the expected cleavage produc...

  19. Evidence for intramolecular self-cleavage of picornaviral replicase precursors.

    OpenAIRE

    Palmenberg, A C; Rueckert, R R

    1982-01-01

    It has previously been shown that when encephalomyocarditis viral RNA is translated in cell-free extracts of rabbit reticulocytes, it synthesizes a virus-coded protease, p22, which is derived by cleavage of a precursor protein, C. Protein C is shown here to be cleaved by two different mechanisms, which were distinguished by their sensitivity to dilution. One mechanism was sensitive to dilution; the other was not. The biphasic cleavage behavior was unchanged by diluting incubation mixtures wit...

  20. Assessment of fracture risk

    Energy Technology Data Exchange (ETDEWEB)

    Kanis, John A. [WHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX (United Kingdom)], E-mail: w.j.pontefract@sheffield.ac.uk; Johansson, Helena; Oden, Anders [WHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX (United Kingdom); McCloskey, Eugene V. [WHO Collaborating Centre for Metabolic Bone Diseases, University of Sheffield Medical School, Beech Hill Road, Sheffield S10 2RX (United Kingdom); Osteoporosis Centre, Northern General Hospital, Sheffield (United Kingdom)

    2009-09-15

    Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

  1. Assessment of fracture risk

    International Nuclear Information System (INIS)

    Fractures are a common complication of osteoporosis. Although osteoporosis is defined by bone mineral density at the femoral neck, other sites and validated techniques can be used for fracture prediction. Several clinical risk factors contribute to fracture risk independently of BMD. These include age, prior fragility fracture, smoking, excess alcohol, family history of hip fracture, rheumatoid arthritis and the use of oral glucocorticoids. These risk factors in conjunction with BMD can be integrated to provide estimates of fracture probability using the FRAX tool. Fracture probability rather than BMD alone can be used to fashion strategies for the assessment and treatment of osteoporosis.

  2. Internal guide RNA interactions interfere with Cas9-mediated cleavage

    Science.gov (United States)

    Thyme, Summer B.; Akhmetova, Laila; Montague, Tessa G.; Valen, Eivind; Schier, Alexander F.

    2016-01-01

    The CRISPR/Cas system uses guide RNAs (gRNAs) to direct sequence-specific DNA cleavage. Not every gRNA elicits cleavage and the mechanisms that govern gRNA activity have not been resolved. Low activity could result from either failure to form a functional Cas9–gRNA complex or inability to recognize targets in vivo. Here we show that both phenomena influence Cas9 activity by comparing mutagenesis rates in zebrafish embryos with in vitro cleavage assays. In vivo, our results suggest that genomic factors such as CTCF inhibit mutagenesis. Comparing near-identical gRNA sequences with different in vitro activities reveals that internal gRNA interactions reduce cleavage. Even though gRNAs containing these structures do not yield cleavage-competent complexes, they can compete with active gRNAs for binding to Cas9. These results reveal that both genomic context and internal gRNA interactions can interfere with Cas9-mediated cleavage and illuminate previously uncharacterized features of Cas9–gRNA complex formation. PMID:27282953

  3. Role of Austenite in Brittle Fracture of Bond Region of Super Duplex Stainless Steel

    Science.gov (United States)

    Kitagawa, Yoshihiko; Ikeuchi, Kenji; Kuroda, Toshio

    Weld simulation of heat-affected zone (HAZ) was performed to investigate the mechanism by which austenite affects the toughness of super duplex stainless steel. Thermal cycles of various peak temperatures in the range from 1373 K to 1673 K corresponding to the HAZ were applied to SAF2507 super duplex stainless steel specimens. Charpy impact test was carried out using the specimens after the weld simulation, and the fracture surfaces were observed by SEM using three-dimensionally reconstruction technique. Austenite content decreased with increasing the peak temperature when the peak temperature exceeded 1473 K and the impact value decreased with increasing the peak temperature and decreasing the austenite content. The thermal cycle of the peak temperature of 1673 K corresponding to weld bond region caused decreasing of austenite content which was 22% lower than that of the base metal. The ductile-brittle transition temperature was measured. As a result the temperature increased rapidly in the weld bond region, the peak temperature of which exceeded 1623 K by the grain growth of ferrite matrix occurring subsequently to the completely dissolution of austenite. The morphology of the fracture surfaces after impact testing at 77 K showed cleavage fracture of ferrite. The {100} orientations of cleavage fracture facets were measured using three-dimensional images of the fracture surfaces and the results were visualized as the orientation color maps. The results showed that there were cleavage fractures consisting of a few facets parallel to each other. It was considered that a few facets existed in one ferrite grain. It was concluded that Widmanstätten austenite divided the large fracture into smaller cleavage facets in a ferrite grain and then suppressed the degradation of bond toughness of duplex stainless steel.

  4. ``Global and local approaches of fracture in the ductile to brittle regime of a low alloy steel``; ``Approches globale et locale de la rupture dans le domaine de transition fragile-ductile d`un acier faiblement allie``

    Energy Technology Data Exchange (ETDEWEB)

    Renevey, S

    1998-12-31

    The study is a contribution to the prediction of flow fracture toughness of low alloy steel and to a better knowledge of fracture behavior in the ductile to brittle transition region. Experiments were performed on a nozzle cut-off from a pressurized water reactor vessel made of steels A508C13 type steel. Axisymmetrical notched specimens were tested to study the fracture onset in a volume element while pre-cracked specimens were used to investigate cleavage fracture after stable crack growth. Systematic observations of fracture surfaces showed manganese sulfide inclusions (MnS) at cleavage sites or in the vicinity. The experimental results were used for modelling by the local approach to fracture. In a volume element the fracture is described by an original probabilistic model. This model is based on volume fraction distributions of MnS inclusions gathered in clusters and on the assumption of a competition without interaction between ductile and cleavage fracture modes. This model was applied to pre-cracked specimens (CT specimens). It is able to describe the scatter in the toughness after a small stable crack growth if a temperature effect on the cleavage stress is assumed. So, the modelling is able to give a lower bound of fracture toughness as a function of temperature. (author) 100 refs.

  5. Cleavage Fracture of Brittle Semiconductors from the Nanometre to the Centimetre Scale

    OpenAIRE

    Wasmer, K; Ballif, Christophe; Gassilloud, R.; Pouvreau, C.; Rabe, R.; Michler, J.; Breguet, J.-M.; Solletti, J.-M.; A. Karimi; Schulz, D

    2008-01-01

    Integrated particle sensors have been developed using thin-film on ASIC technology. For this purpose, hydrogenated amorphous silicon diodes, in various configurations, have been optimized for particle detection. These devices were first deposited on glass substrates to optimize the material properties and the dark current of very thick diodes (with thickness up to 50 μm). Corresponding diodes were later directly deposited on CMOS readout chips. These integrated particle sensors have been char...

  6. Imaging of vertebral fractures

    Directory of Open Access Journals (Sweden)

    Ananya Panda

    2014-01-01

    Full Text Available Vertebral fracture is a common clinical problem. Osteoporosis is the leading cause of non-traumatic vertebral fracture. Often, vertebral fractures are not clinically suspected due to nonspecific presentation and are overlooked during routine interpretation of radiologic investigations. Moreover, once detected, many a times the radiologist fails to convey to the clinician in a meaningful way. Hence, vertebral fractures are a constant cause of morbidity and mortality. Presence of vertebral fracture increases the chance of fracture in another vertebra and also increases the risk of subsequent hip fracture. Early detection can lead to immediate therapeutic intervention improving further the quality of life. So, in this review, we wish to present a comprehensive overview of vertebral fracture imaging along with an algorithm of evaluation of vertebral fractures.

  7. Fracture Criterion for Fracture Mechanics of Magnets

    Institute of Scientific and Technical Information of China (English)

    潘灏; 杨文涛

    2003-01-01

    The applicability and limitation of some fracture criteria in the fracture mechanics of magnets are studied.It is shown that the magnetic field intensity factor can be used as a fracture criterion when the crack in a magnet is only affected by a magnetic field. For some magnetostrictive materials in which the components of magnetostriction strain do not satisfy the compatibility equation of deformation, the stress intensity factor can no longer be effectively applicable as a fracture criterion when the crack in a magnet is affected by a magnetic field and mechanical loads simultaneously.

  8. Small molecule activators of pre-mRNA 3′ cleavage

    OpenAIRE

    Ryan, Kevin; Khleborodova, Asya; Pan, Jingyi; Ryan, Xiaozhou P.

    2009-01-01

    3′ Cleavage and polyadenylation are obligatory steps in the biogenesis of most mammalian pre-mRNAs. In vitro reconstitution of the 3′ cleavage reaction from human cleavage factors requires high concentrations of creatine phosphate (CP), though how CP activates cleavage is not known. Previously, we proposed that CP might work by competitively inhibiting a cleavage-suppressing serine/threonine (S/T) phosphatase. Here we show that fluoride/EDTA, a general S/T phosphatase inhibitor, activates in ...

  9. Introduction into fracture mechanics

    International Nuclear Information System (INIS)

    The present report gives an introduction to the basic principles of fracture mechanics. First the behaviour of a linear elastic body containing a crack is described. This is followed by a survey of experimental methods for the determination of fracture mechanics properties, like R-curve and fatigue crack growth. Two chapters deal with the most important parameters affecting stable crack growth and fracture toughness. The knowledge of the limits of applicability of linear eleastic fracture mechanics and of the concepts of elastic-plastic fracture mechanics is of particular importance. The last chapter deals with some basic procedures for the practical application of fracture mechanics. (orig.)

  10. Mechanism of intramembrane cleavage of alcadeins by γ-secretase.

    Directory of Open Access Journals (Sweden)

    Yi Piao

    Full Text Available BACKGROUND: Alcadein proteins (Alcs; Alcα, Alcβand Alcγ are predominantly expressed in neurons, as is Alzheimer's β-amyloid (Aβ precursor protein (APP. Both Alcs and APP are cleaved by primary α- or β-secretase to generate membrane-associated C-terminal fragments (CTFs. Alc CTFs are further cleaved by γ-secretase to secrete p3-Alc peptide along with the release of intracellular domain fragment (Alc ICD from the membrane. In the case of APP, APP CTFβ is initially cleaved at the ε-site to release the intracellular domain fragment (AICD and consequently the γ-site is determined, by which Aβ generates. The initial ε-site is thought to define the final γ-site position, which determines whether Aβ40/43 or Aβ42 is generated. However, initial intracellular ε-cleavage sites of Alc CTF to generate Alc ICD and the molecular mechanism that final γ-site position is determined remains unclear in Alcs. METHODOLOGY: Using HEK293 cells expressing Alcs plus presenilin 1 (PS1, a catalytic unit of γ-secretase and the membrane fractions of these cells, the generation of p3-Alc possessing C-terminal γ-cleavage site and Alc ICD possessing N-terminal ε-cleavage site were analysed with MALDI-TOF/MS. We determined the initial ε-site position of all Alcα, Alcβ and Alcγ, and analyzed the relationship between the initially determined ε-site position and the final γ-cleavage position. CONCLUSIONS: The initial ε-site position does not always determine the final γ-cleavage position in Alcs, which differed from APP. No additional γ-cleavage sites are generated from artificial/non-physiological positions of ε-cleavage for Alcs, while the artificial ε-cleavage positions can influence in selection of physiological γ-site positions. Because alteration of γ-secretase activity is thought to be a pathogenesis of sporadic Alzheimer's disease, Alcs are useful and sensitive substrate to detect the altered cleavage of substrates by γ-secretase, which may

  11. Pripper: prediction of caspase cleavage sites from whole proteomes

    Directory of Open Access Journals (Sweden)

    Salmi Jussi

    2010-06-01

    Full Text Available Abstract Background Caspases are a family of proteases that have central functions in programmed cell death (apoptosis and inflammation. Caspases mediate their effects through aspartate-specific cleavage of their target proteins, and at present almost 400 caspase substrates are known. There are several methods developed to predict caspase cleavage sites from individual proteins, but currently none of them can be used to predict caspase cleavage sites from multiple proteins or entire proteomes, or to use several classifiers in combination. The possibility to create a database from predicted caspase cleavage products for the whole genome could significantly aid in identifying novel caspase targets from tandem mass spectrometry based proteomic experiments. Results Three different pattern recognition classifiers were developed for predicting caspase cleavage sites from protein sequences. Evaluation of the classifiers with quality measures indicated that all of the three classifiers performed well in predicting caspase cleavage sites, and when combining different classifiers the accuracy increased further. A new tool, Pripper, was developed to utilize the classifiers and predict the caspase cut sites from an arbitrary number of input sequences. A database was constructed with the developed tool, and it was used to identify caspase target proteins from tandem mass spectrometry data from two different proteomic experiments. Both known caspase cleavage products as well as novel cleavage products were identified using the database demonstrating the usefulness of the tool. Pripper is not restricted to predicting only caspase cut sites, but it gives the possibility to scan protein sequences for any given motif(s and predict cut sites once a suitable cut site prediction model for any other protease has been developed. Pripper is freely available and can be downloaded from http://users.utu.fi/mijopi/Pripper. Conclusions We have developed Pripper, a tool for

  12. Cell-surface acceleration of urokinase-catalyzed receptor cleavage

    DEFF Research Database (Denmark)

    Høyer-Hansen, G; Ploug, M; Behrendt, N;

    1997-01-01

    or indirectly mediated by uPA itself. In a soluble system, uPA can cleave purified uPAR, but the low efficiency of this reaction has raised doubts as to whether uPA is directly responsible for uPAR cleavage on the cells. We now report that uPA-catalyzed cleavage of uPAR on the cell surface is...... strongly favored relative to the reaction in solution. The time course of uPA-catalyzed cleavage of cell-bound uPAR was studied using U937 cells stimulated with phorbol 12-myristate 13-acetate. Only 30 min was required for 10 nM uPA to cleave 50% of the cell-bound uPAR. This uPA-catalyzed cleavage reaction...... was inhibited by a prior incubation of the cells with uPA inactivated by diisopropyl fluorophosphate, demonstrating a requirement for specific receptor binding of the active uPA to obtain the high-efficiency cleavage of cell-bound uPAR. Furthermore, amino-terminal sequence analysis revealed that u...

  13. The effect of specimen and flaw dimensions on fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Nevalainen, M.J. [VTT Manufacturing Technology, Espoo (Finland)

    1997-06-01

    The effect of the specimen size and geometry on fracture toughness has been investigated both by experimental tests and computational analyses. The methods for constraint description, namely T-stress, Q-parameter and Small-Scale Yielding Correction (SSYC) have been compared and applied for various geometries. A statistical treatment for the specimen thickness effect on cleavage fracture toughness has been investigated. Elliptical surface cracks were compared with straight-thickness cracks and a method for crack shape correction was presented. Based on the results, the differences in apparent fracture toughness values obtained from various specimen configurations can be better understood and taken into account. 64 refs. The thesis includes also four previous publications by author.

  14. Plastic deformation and fracture behaviour of 21/4 Cr-1 Mo pressure-vessel steel

    International Nuclear Information System (INIS)

    During the heat treatment of steel plates and forgings of large thicknesses, microstructures with various volume fractions of ferrite appear. Plastic properties and fracture behaviour of these mixed microstructures are a function of ferrite content. The influence of ferrite content in the range from 0% to 54% in the bainitic-ferritic microstructure on mechanical properties and fracture behaviour of 21/4 Cr-1 Mo steel was examined. The yield stress was found to decrease linearly with the volume fraction of ferrite. The tensile strength was independent of ferrite content up to 25%, after which the tensile strength decreased. Using the Charpy test it has been found that the critical ferrite content-25%-exists in a mixed microstructure, at which the propagation and initiation transition temperatures attain the highest values. The fracture toughness tests gave the same results. Increasing the volume fraction of ferrite, the cleavage fracture toughness/temperature curves were shifted to higher temperatures. Simultaneously, the ductile-brittle fracture toughness transition temperature was raised reaching the highest value for the critical ferrite content. The fracture behaviour could be tentatively explained through the influence of ferrite volume fraction on both the cleavage fracture stress and the stress level at the crack tip. (author)

  15. A study of fracture of cast duplex stainless steels embrittled by aging at 400 C

    International Nuclear Information System (INIS)

    This work deals in particular with the fracture at 20 C of a cast duplex stainless steel ZCND19-10M containing 20% of ferrite and aged at 400 C during 700 h in order to obtain a fracture criterion of a volume element, in the framework of the local approach to fracture. With tensile tests on axisymmetric coped test pieces it is possible to study the effect of the stresses triaxiality on ductility. The fracture mechanisms are studied on metallographic sections and of fracture surface analyses. Cleavage cracks are initiated in ferrite and end in austenite. They grow up by blunting in austenite, and then form a macro-crack by coalescence. These cleavage cracks are clustered together. A crystallographic study shows that they appear in austenite grains which deform with simple slide, the incompatibility stress between the two phases being higher in this case. At a superior scale, the mechanical analysis of the crack growth conditions, shows that it is controlled by the plastic deformation. Moreover, cracks appear progressively when the deformation increases. A Gurson porous material behaviour model has been used to simulate the ductile fracture of this material. With random selection of grains strongly damaged (crack clusters) in coped specimens and of finite element calculations of these same specimens, it has been shown that ductility is controlled by cluster fracture and that its great dispersion can be correctly reproduced. (O.M.)

  16. Multi scale study of the plasticity at low temperature in {alpha}-iron: application for the cleavage; Etude multiechelle de la plasticite du fer-{alpha} a basse temperature application au clivage

    Energy Technology Data Exchange (ETDEWEB)

    Chaussidon, J

    2007-10-15

    An accident inside a nuclear power plant may lead to the cleavage of the nuclear vessel made of bainitic steel. In order to understand the origin of this fracture, we studied BCC-iron plasticity at low temperature using numerical simulations at different scales. Molecular Dynamics simulations show the high dependency of screw dislocation motion with temperature and stress. Results from these simulations were added to experiment data to develop a new Dislocation Dynamics code dedicated to BCC iron at low temperature. The code was used to model plasticity into a ferritic lath for various temperatures. This work confirms that cleavage is favoured by low temperatures. (author)

  17. Short RNA guides cleavage by eukaryotic RNase III.

    Directory of Open Access Journals (Sweden)

    Bruno Lamontagne

    Full Text Available In eukaryotes, short RNAs guide a variety of enzymatic activities that range from RNA editing to translation repression. It is hypothesized that pre-existing proteins evolved to bind and use guide RNA during evolution. However, the capacity of modern proteins to adopt new RNA guides has never been demonstrated. Here we show that Rnt1p, the yeast orthologue of the bacterial dsRNA-specific RNase III, can bind short RNA transcripts and use them as guides for sequence-specific cleavage. Target cleavage occurred at a constant distance from the Rnt1p binding site, leaving the guide RNA intact for subsequent cleavage. Our results indicate that RNase III may trigger sequence-specific RNA degradation independent of the RNAi machinery, and they open the road for a new generation of precise RNA silencing tools that do not trigger a dsRNA-mediated immune response.

  18. Analytical model for intergrain expansion and cleavage: random grain boundaries

    International Nuclear Information System (INIS)

    A description of rigid-body grain boundary relaxation and cleavage in tungsten is performed using a pair-wise Morse interatomic potential in real and reciprocal spaces. Cleavage energies and grain boundary dilatation of random grain boundaries were formulated and computed using atomic layer interaction energies. These values were determined using a model for a relaxed random grain boundary that consists of rigid grains on either side of the boundary plane that are allowed to float to reach the equilibrium position. Expressions are given that describe in real space the energy of interatomic interaction on random grain boundaries with twist orientation. It was shown that grain-boundary expansion and cleavage energies of the most widespread random grain boundaries are mainly determined by grain boundary atomic density

  19. A new cultural cleavage in post-modern society

    Directory of Open Access Journals (Sweden)

    Jan-Erik Lane

    2007-09-01

    Full Text Available The attitudes towards gender and homosexuality tend to be linked at the micro level (individuals, which explains the political saliency of this newly emerging cleavage. At the macro level (country, the main finding is that the value orientations towards gender and homosexuality are strongly embedded in the basic cultural or civilisation differences among countries. As developing countries modernise and enter post-modernity, they will also experience the gender cleavage, especially when they adhere to an individualistic culture. Cultural cleavages in the post-modern society, whether in rich or developing countries, can only be properly researched by the survey method. It opens up a large area for both micro and macro analyses in the social sciences.

  20. Hip fracture surgery

    Science.gov (United States)

    ... repair; Femoral neck fracture repair; Trochanteric fracture repair; Hip pinning surgery; Osteoarthritis-hip ... top of the bone) you may have a hip pinning procedure. During this surgery: You lie on ...

  1. Fractures in anisotropic media

    Science.gov (United States)

    Shao, Siyi

    Rocks may be composed of layers and contain fracture sets that cause the hydraulic, mechanical and seismic properties of a rock to be anisotropic. Coexisting fractures and layers in rock give rise to competing mechanisms of anisotropy. For example: (1) at low fracture stiffness, apparent shear-wave anisotropy induced by matrix layering can be masked or enhanced by the presence of a fracture, depending on the fracture orientation with respect to layering, and (2) compressional-wave guided modes generated by parallel fractures can also mask the presence of matrix layerings for particular fracture orientations and fracture specific stiffness. This report focuses on two anisotropic sources that are widely encountered in rock engineering: fractures (mechanical discontinuity) and matrix layering (impedance discontinuity), by investigating: (1) matrix property characterization, i.e., to determine elastic constants in anisotropic solids, (2) interface wave behavior in single-fractured anisotropic media, (3) compressional wave guided modes in parallel-fractured anisotropic media (single fracture orientation) and (4) the elastic response of orthogonal fracture networks. Elastic constants of a medium are required to understand and quantify wave propagation in anisotropic media but are affected by fractures and matrix properties. Experimental observations and analytical analysis demonstrate that behaviors of both fracture interface waves and compressional-wave guided modes for fractures in anisotropic media, are affected by fracture specific stiffness (controlled by external stresses), signal frequency and relative orientation between layerings in the matrix and fractures. A fractured layered medium exhibits: (1) fracture-dominated anisotropy when the fractures are weakly coupled; (2) isotropic behavior when fractures delay waves that are usually fast in a layered medium; and (3) matrix-dominated anisotropy when the fractures are closed and no longer delay the signal. The

  2. Fracture toughness correlations

    International Nuclear Information System (INIS)

    In this study existing fracture parameter correlations are reviewed. Their applicability and reliability are discussed in detail. A new KIC-CVN-correlation, based on a theoretical brittle fracture model, is presented

  3. Metatarsal stress fractures - aftercare

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000553.htm Metatarsal stress fractures - aftercare To use the sharing features on ... that connect your ankle to your toes. A stress fracture is a break in the bone that ...

  4. Fractures in childhood

    International Nuclear Information System (INIS)

    Clinical diagnosis of fractures in childhood can be very difficult. Therefore imaging, not only x-rays but also ultrasound, computed tomography and magnetic resonance imaging are of special importance. There are typical pediatric types of fractures due to epiphyseal plates and high flexibility of the bone. Fractures heal faster and dislocations can be spontaneously corrected better but also growth disturbance can occur. The second part of the article describes the special types of fractures with special attention to the characteristics in childhood.

  5. Individualizing fracture risk prediction

    OpenAIRE

    van Geel, Tineke A. C. M.; van den Bergh, Joop P. W.; Dinant, Geert Jan; Geusens, Piet

    2010-01-01

    Low bone mineral density (BMD) and clinical factors (CRF) have been identified as factors associated with an increased relative risk of fractures. From this observation and for clinical decision making, the concept of prediction of the individual absolute risk of fractures has emerged. It refers to the individual's risk for fractures over a certain time period, e.g. the next 5 and 10 years. Two individualized fracture risk calculation tools that are increasingly used and are available on the ...

  6. Synthesis, antioxidant and DNA cleavage activities of novel indole derivatives.

    Science.gov (United States)

    Biradar, J S; Sasidhar, B S; Parveen, R

    2010-09-01

    A new series of novel indole derivatives containing barbitone moiety (5a-i) are synthesized by simple and efficient condensation of chalcones (3a-i) with barbituric acid (4). The synthesized compounds are screened for their antioxidant (free radical scavenging, total antioxidant capacity and ferric reducing antioxidant power) and DNA cleavage activities were evaluated. Among the synthesized compounds (5a), (5d) and (5g) exhibited excellent antioxidant activity and all the tested compounds in the series have exhibited promising DNA cleavage activities. The structures of the synthesized compounds are assigned on the basis of elemental analysis, IR, (1)H NMR, (13)C NMR and mass spectral data. PMID:20594623

  7. Sensitive and fast mutation detection by solid phase chemical cleavage

    DEFF Research Database (Denmark)

    Hansen, Lise Lotte; Justesen, Just; Kruse, Torben A

    1996-01-01

    We have developed a solid phase chemical cleavage method (SpCCM) for screening large DNA fragments for mutations. All reactions can be carried out in microtiterwells from the first amplification of the patient (or test) DNA through the search for mutations. The reaction time is significantly...... reduced compared to the conventional chemical cleavage method (CCM), and even by using a uniformly labelled probe, the exact position and nature of the mutation can be revealed. The SpCCM is suitable for automatization using a workstation to carry out the reactions and a fluorescent detection-based DNA...

  8. Micro-scale fracture experiments on zirconium hydrides and phase boundaries

    Science.gov (United States)

    Chan, H.; Roberts, S. G.; Gong, J.

    2016-07-01

    Fracture properties of micro-scale zirconium hydrides and phase boundaries were studied using microcantilever testing methods. FIB-machined microcantilevers were milled on cross-sectional surfaces of hydrided samples, with the most highly-stressed regions within the δ-hydride film, within the α-Zr or along the Zr-hydride interface. Cantilevers were notched using the FIB and then tested in bending using a nanoindenter. Load-displacement results show that three types of cantilevers have distinct deformation properties. Zr cantilevers deformed plastically. Hydride cantilevers fractured after a small amount of plastic flow; the fracture toughness of the δ-hydride was found to be 3.3 ± 0.4 MPam1/2 and SEM examination showed transgranular cleavage on the fracture surfaces. Cantilevers notched at the Zr-hydride interface developed interfacial voids during loading, at loads considerably lower than that which initiate brittle fracture of hydrides.

  9. Microstructure evolution and fracture behaviour for electron beam welding of Ti–6Al–4V

    Indian Academy of Sciences (India)

    Wu Huiqiang; Feng Jicai; He Jingshan

    2004-08-01

    The effect of microstructural characteristics on fracture behaviour mechanism for electron beam welding of Ti–6Al–4V was investigated. The results indicated that the welded microstructure composed of coarse needle + phases presenting disordered and multidirectional short needle morphology to make fracture mechanism complex. The coarse grains in weld seam with microhardness 536 HV were easy to be fractured in the region where welding heat input was ≥ 68.8 kJ/m. There exists flat curves of Ti, Al and V, Fe concentration distribution fluctuation to cause microstructural amplitude-modulated decomposition to increase the joint ductility and cleavage strength. The uneven distribution of the partial micropores located at the interior of the specimen acting as crack initiation sites lead to non-linear branch propagating path. The + interlaced structure results in the fracture location near / interface. The existence of stacking fault structure caused pile-up of dislocation to produce micropores to be new fracture initiation sites.

  10. Role of MRI in hip fractures, including stress fractures, occult fractures, avulsion fractures

    Energy Technology Data Exchange (ETDEWEB)

    Nachtrab, O. [Department of Radiology, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Gobowen, Oswestry Shropshire SY10 7AG (United Kingdom); Cassar-Pullicino, V.N., E-mail: Victor.Pullicino@rjah.nhs.uk [Department of Radiology, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Gobowen, Oswestry Shropshire SY10 7AG (United Kingdom); Lalam, R.; Tins, B.; Tyrrell, P.N.M.; Singh, J. [Department of Radiology, The Robert Jones and Agnes Hunt Orthopaedic Hospital, Gobowen, Oswestry Shropshire SY10 7AG (United Kingdom)

    2012-12-15

    MR imaging plays a vital role in the diagnosis and management of hip fractures in all age groups, in a large spectrum of patient groups spanning the elderly and sporting population. It allows a confident exclusion of fracture, differentiation of bony from soft tissue injury and an early confident detection of fractures. There is a spectrum of MR findings which in part is dictated by the type and cause of the fracture which the radiologist needs to be familiar with. Judicious but prompt utilisation of MR in patients with suspected hip fractures has a positive therapeutic impact with healthcare cost benefits as well as social care benefits.

  11. Role of MRI in hip fractures, including stress fractures, occult fractures, avulsion fractures

    International Nuclear Information System (INIS)

    MR imaging plays a vital role in the diagnosis and management of hip fractures in all age groups, in a large spectrum of patient groups spanning the elderly and sporting population. It allows a confident exclusion of fracture, differentiation of bony from soft tissue injury and an early confident detection of fractures. There is a spectrum of MR findings which in part is dictated by the type and cause of the fracture which the radiologist needs to be familiar with. Judicious but prompt utilisation of MR in patients with suspected hip fractures has a positive therapeutic impact with healthcare cost benefits as well as social care benefits.

  12. TEM in situ observation of fracture behavior in ceramic materials

    International Nuclear Information System (INIS)

    The atomic structures of crack walls due to cleavage fracture in silicon nitride (Si3N4) and magnesium oxide (MgO) have been investigated by in situ straining transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM) at room temperature. In the case of Si3N4, the crack walls on the (11-bar 00) plane were atomically flat, which indicates that the crack propagated along a particular crystal plane without deflection. On the other hand, the cleaved crack walls in MgO were not atomically flat but contained a number of square-shaped steps with a few {010} atomic layers in height. Thus, it can be said that the cleavage crack was deflected at the atomic level during its rapid propagation. The origin of their step structures is discussed using results from molecular dynamics (MD) simulations

  13. Orbital fractures: a review

    Directory of Open Access Journals (Sweden)

    Jeffrey M Joseph

    2011-01-01

    Full Text Available Jeffrey M Joseph, Ioannis P GlavasDivision of Ophthalmic Plastic and Reconstructive Surgery, Department of Ophthalmology, School of Medicine, New York University, New York, NY, USA; Manhattan Eye, Ear, and Throat Hospital, New York, NY, USAAbstract: This review of orbital fractures has three goals: 1 to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2 to explain how to assess and examine a patient after periorbital trauma, and 3 to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training.Keywords: orbit, trauma, fracture, orbital floor, medial wall, zygomatic, zygomatic complex, zmc fracture, zygomaticomaxillary complex fractures 

  14. Mechanics of Hydraulic Fractures

    Science.gov (United States)

    Detournay, Emmanuel

    2016-01-01

    Hydraulic fractures represent a particular class of tensile fractures that propagate in solid media under pre-existing compressive stresses as a result of internal pressurization by an injected viscous fluid. The main application of engineered hydraulic fractures is the stimulation of oil and gas wells to increase production. Several physical processes affect the propagation of these fractures, including the flow of viscous fluid, creation of solid surfaces, and leak-off of fracturing fluid. The interplay and the competition between these processes lead to multiple length scales and timescales in the system, which reveal the shifting influence of the far-field stress, viscous dissipation, fracture energy, and leak-off as the fracture propagates.

  15. Fe-Catalyzed Oxidative Cleavage of Unsaturated Fatty Acids

    NARCIS (Netherlands)

    Spannring, P.

    2013-01-01

    The oxidative cleavage of unsaturated fatty acids into aldehydes or carboxylic acids gives access to valuable products. The products can be used as chemical building blocks, as emulsifiers or in the paint or polymer industry. Ozonolysis is applied industrially to cleave the fatty acid oleic acid int

  16. Perceiving Social Cleavages and Inequalities: The Case of Israeli Adolescents.

    Science.gov (United States)

    Dar, Yechezkel; Erhard, Rachel; Resh, Nura

    1998-01-01

    An analysis of perceptions of social cleavage and inequality among approximately 9000 Israeli eighth and ninth graders showed students accurately comprehended a multifaceted society with major social divisions. A social map with inequality was revealed in which ethnicity played the least prominent role. Personal and social traits influenced…

  17. The pattern of DNA cleavage intensity around indels.

    Science.gov (United States)

    Chen, Wei; Zhang, Liqing

    2015-01-01

    Indels (insertions and deletions) are the second most common form of genetic variations in the eukaryotic genomes and are responsible for a multitude of genetic diseases. Despite its significance, detailed molecular mechanisms for indel generation are still unclear. Here we examined 2,656,597 small human and mouse germline indels, 16,742 human somatic indels, 10,599 large human insertions, and 5,822 large chimpanzee insertions and systematically analyzed the patterns of DNA cleavage intensities in the 200 base pair regions surrounding these indels. Our results show that DNA cleavage intensities close to the start and end points of indels are significantly lower than other regions, for both small human germline and somatic indels and also for mouse small indels. Compared to small indels, the patterns of DNA cleavage intensity around large indels are more complex, and there are two low intensity regions near each end of the indels that are approximately 13 bp apart from each other. Detailed analyses of a subset of indels show that there is slight difference in cleavage intensity distribution between insertion indels and deletion indels that could be contributed by their respective enrichment of different repetitive elements. These results will provide new insight into indel generation mechanisms. PMID:25660536

  18. Cleavage sites within the poliovirus capsid protein precursors

    International Nuclear Information System (INIS)

    Partial amino-terminal sequence analysis was performed on radiolabeled poliovirus capsid proteins VP1, VP2, and VP3. A computer-assisted comparison of the amino acid sequences obtained with that predicted by the nucleotide sequence of the poliovirus genome allows assignment of the amino terminus of each capsid protein to a unique position within the virus polyprotein. Sequence analysis of trypsin-digested VP4, which has a blocked amino terminus, demonstrates that VP4 is encoded at or very near to the amino terminus of the polyprotein. The gene order of the capsid proteins is VP4-VP2-VP3-VP1. Cleavage of VP0 to VP4 and VP2 is shown to occur between asparagine and serine, whereas the cleavages that separate VP2/VP3 and VP3/VP1 occur between glutamine and glycine residues. This finding supports the hypothesis that the cleavage of VP0, which occurs during virion morphogenesis, is distinct from the cleavages that separate functional regions of the polyprotein

  19. Selective cleavage enhanced by acetylating the side chain of lysine.

    Science.gov (United States)

    Fu, Leixiaomeng; Chen, Tingting; Xue, Gaiqing; Zu, Lily; Fang, Weihai

    2013-01-01

    Selective cleavage is of great interest in mass spectrometry studies as it can help sequence identification by promoting simple fragmentation pattern of peptides and proteins. In this work, the collision-induced dissociation of peptides containing internal lysine and acetylated lysine residues were studied. The experimental and computational results revealed that multiple fragmentation pathways coexisted when the lysine residue was two amino acid residues away from N-terminal of the peptide. After acetylation of the lysine side-chain, b(n)+ ions were the most abundant primary fragment products and the Lys(Ac)-Gly amide bond became the dominant cleavage site via an oxazolone pathway. Acetylating the side-chain of lysine promoted the selective cleavage of Lys-Xxx amide bond and generated much more information of the peptide backbone sequence. The results re-evaluate the selective cleavage due to the lysine basic side-chain and provide information for studying the post-translational modification of proteins and other bio-molecules containing Lys residues. PMID:23303756

  20. Phosphate diester cleavage promoted by the novel artificial biomimetic agent

    Czech Academy of Sciences Publication Activity Database

    Bím, Daniel; Rulíšek, Lubomír; Hodačová, J.

    Praha: Czech Chemical Society, 2014. s. 51. [Liblice 2014. Advances in Organic, Bioorganic and Pharmaceutical Chemistry /49./. 07.11.2014-09.11.2014, Lázně Bělohrad] Institutional support: RVO:61388963 Keywords : phosphate diesters * bond cleavage Subject RIV: CF - Physical ; Theoretical Chemistry

  1. Modeling Radial Holoblastic Cleavage: A Laboratory Activity for Developmental Biology.

    Science.gov (United States)

    Ellis, Linda K.

    2000-01-01

    Introduces a laboratory activity designed for an undergraduate developmental biology course. Uses Play-Doh (plastic modeling clay) to build a multicellular embryo in order to provide a 3-D demonstration of cleavage. Includes notes for the instructor and student directions. (YDS)

  2. Sequence specific inhibition of DNA restriction enzyme cleavage by PNA

    DEFF Research Database (Denmark)

    Nielsen, P.E.; Egholm, M.; Berg, R.H.;

    1993-01-01

    Plasmids containing double-stranded 10-mer PNA (peptide nucleic acid chimera) targets proximally flanked by two restriction enzyme sites were challenged with the complementary PNA or PNAs having one or two mismatches, and the effect on the restriction enzyme cleavage of the flanking sites was...

  3. Rhodium-catalyzed C-C bond cleavage reactions

    Czech Academy of Sciences Publication Activity Database

    Nečas, D.; Kotora, Martin

    2007-01-01

    Roč. 11, č. 17 (2007), s. 1566-1591. ISSN 1385-2728 Institutional research plan: CEZ:AV0Z40550506 Keywords : rhodium * catalysis * C-C bond cleavage Subject RIV: CC - Organic Chemistry Impact factor: 3.961, year: 2007

  4. Modeling of Interaction of Hydraulic Fractures in Complex Fracture Networks

    Science.gov (United States)

    Kresse, O. 2; Wu, R.; Weng, X.; Gu, H.; Cohen, C.

    2011-12-01

    A recently developed unconventional fracture model (UFM) is able to simulate complex fracture network propagation in a formation with pre-existing natural fractures. Multiple fracture branches can propagate at the same time and intersect/cross each other. Each open fracture exerts additional stresses on the surrounding rock and adjacent fractures, which is often referred to as "stress shadow" effect. The stress shadow can cause significant restriction of fracture width, leading to greater risk of proppant screenout. It can also alter the fracture propagation path and drastically affect fracture network patterns. It is hence critical to properly model the fracture interaction in a complex fracture model. A method for computing the stress shadow in a complex hydraulic fracture network is presented. The method is based on an enhanced 2D Displacement Discontinuity Method (DDM) with correction for finite fracture height. The computed stress field is compared to 3D numerical simulation in a few simple examples and shows the method provides a good approximation for the 3D fracture problem. This stress shadow calculation is incorporated in the UFM. The results for simple cases of two fractures are presented that show the fractures can either attract or expel each other depending on their initial relative positions, and compares favorably with an independent 2D non-planar hydraulic fracture model. Additional examples of both planar and complex fractures propagating from multiple perforation clusters are presented, showing that fracture interaction controls the fracture dimension and propagation pattern. In a formation with no or small stress anisotropy, fracture interaction can lead to dramatic divergence of the fractures as they tend to repel each other. However, when stress anisotropy is large, the fracture propagation direction is dominated by the stress field and fracture turning due to fracture interaction is limited. However, stress shadowing still has a strong effect

  5. Stress fractures in athletes.

    Science.gov (United States)

    Hulkko, A; Orava, S

    1987-06-01

    During the 14-year period of 1971-1985, 368 stress fractures in 324 athletes were treated. The series contained 268 fractures in males and 100 fractures in females; 32 fractures occurred in children (less than 16 years), 117 in adolescents (16-19 years), and 219 in adults. Forty-six fractures were incurred by athletes at an international level, 274 by athletes at a national or district level and 48 by recreational athletes. Of the total cases, 72% occurred to runners and a further 12% to athletes in other sports after running exercises. The distribution of the stress fractures by site was: tibia 182, metatarsal bones 73, fibula 44, big toe sesamoid bones 15, femoral shaft 14, femoral neck 9, tarsal navicular 9, pelvis 7, olecranon 5 and other bones 10. Of the total fractures, 342 were treated conservatively and 26 fractures required surgical treatment. The operative indication was dislocation in 5 cases and delayed union/nonunion in 21 cases. The sites most often affected by delayed union were: anterior midtibia, sesamoid bones of the big toe, base of the fifth metatarsal, olecranon, and tarsal navicular. The athletes at an international level experienced the greatest risk of multiple separate fractures, protracted healing, or fractures requiring surgery. PMID:3623785

  6. School Desegregation and Racial Cleavage, 1954-1970: A Review of the Literature

    Science.gov (United States)

    Carithers, Martha W.

    1970-01-01

    Reviews the empirical studies dealing with school desegregation and racial cleavage which have appeared since the 1954 Supreme Court decision. Focuses on patterns and consequences of interracial association, and attitude change relevant to racial cleavage. (DM)

  7. The effect of structure in a long target RNA on ribozyme cleavage efficiency.

    OpenAIRE

    Campbell, T B; McDonald, C K; Hagen, M.

    1997-01-01

    Inhibition of gene expression by catalytic RNA (ribozymes) requires that ribozymes efficiently cleave specific sites within large target RNAs. However, the cleavage of long target RNAs by ribozymes is much less efficient than cleavage of short oligonucleotide substrates because of higher order structure in the long target RNA. To further study the effects of long target RNA structure on ribozyme cleavage efficiency, we determined the accessibility of seven hammerhead ribozyme cleavage sites i...

  8. Mutational analysis of a type II topoisomerase cleavage site: distinct requirements for enzyme and inhibitors.

    OpenAIRE

    Freudenreich, C H; Kreuzer, K. N.

    1993-01-01

    We have analyzed the DNA sequence requirements for cleavage of a 30 bp oligonucleotide that contains a strong bacteriophage T4 type II topoisomerase site. A novel method was used to generate substrates with each of the four nucleotides at 10 positions surrounding the cleavage site, and mutant substrates were also prepared for the four internal positions of the staggered cleavage site. The substrates were tested for cleavage in the presence of several inhibitors that induce enzyme-mediated cle...

  9. Cleavage patterns and the topology of the metazoan tree of life

    OpenAIRE

    Valentine, James W.

    1997-01-01

    Several major alliances of metazoan phyla have been identified by small subunit rRNA sequence comparisons. It is possible to arrange the phyla to produce a parsimonious distribution of cleavage types, requiring only one change from a radial ancestral condition to spiral cleavage and one other to “idiosyncratic” cleavage; this arrangement is consistent with most of the recent molecular phylogenies. The cleavage shifts are correlated with changes in many of the features that once were used to d...

  10. Geostatistics for fracture characterization

    International Nuclear Information System (INIS)

    As the critical role of fractures has become more apparent in fluid flow and contaminant transport studies, the characterization of fracture networks has received considerable attention in a wide variety of applications such as nuclear waste repository design. The application of geostatistics to fracture characterization has traditionally involved modelling fractures as thin disks; assumptions about the frequency, orientation, length and width of these disks allow the construction of a 3D model of the fracture network. This paper examines alternatives whose statistical parameters are more relevant for contaminant transport studies and are also easier to infer and validate. A new algorithm for conditional simulation is presented, one that is able to honor multipoint statistics through annealing. By honoring statistics that capture with two-point spatial convariances, this algorithm offers an important new tool not only for the specific problem of fracture characterization but also for the more general problem of spatial simulation

  11. An Examination Of Fracture Splitting Parameters Of Crackable Connecting Rods

    Directory of Open Access Journals (Sweden)

    Zafer Özdemir

    2000-06-01

    Full Text Available Fracture splitting method is an innovative processing technique in the field of automobile engine connecting rod (con/rod manufacturing. Compared with traditional method, this technique has remarkable advantages. Manufacturing procedures, equipment and tools investment can be decreased and energy consumption reduced remarkably. Furthermore, product quality and bearing capability can also be improved. It provides a high quality, high accuracy and low cost route for producing connecting rods (con/rods. With the many advantages mentioned above, this method has attracted manufacturers attention and has been utilized in many types of con/rod manufacturing. In this article, the method and the advantages it provides, such as materials, notches for fracture splitting, fracture splitting conditions and fracture splitting equipment are discussed in detail. The paper describes an analysis of examination of fracture splitting parameters and optik-SEM fractography of C70S6 crackable connectıng rod. Force and velocity parameters are investigated. That uniform impact force distrubition starting from the starting notch causes brittle and cleavage failure mode is obtained as a result. This induces to decrease the toughness.

  12. Pediatric stress fractures

    OpenAIRE

    de la Cuadra, P.; Albiñana, J.

    2000-01-01

    Stress fractures in children are uncommon. This report describes the findings of 8 cases in 6 children. One patient had 3 stress fractures: 2 consecutive midshaft stress fractures of the same tibia associated with one of the fibula. Signs and symptoms may be misdiagnosed as malignant tumors or osteomyelitis. Serial radiographs and computed tomography scans are the key to the diagnosis, although bone scan and magnetic resonance imaging can be helpful. Biopsy is unnecessary and might even be mi...

  13. Bone fractures after menopause

    OpenAIRE

    Barlow, David H.; Bouchard, Philippe; Brandi, Maria Luisa; Evers, J.L.H.; Glasier, A.; Negri, Eva; Papapoulos, Socrates E; Ralston, Stuart H; Rizzoli, Rene; Baird, D T; Collins, J.; G. Benagiano; P.G. Crosignani; La Vecchia, C.; Volpe, A

    2010-01-01

    Every year 30% of individuals above age 65 fall, and falls are the principal cause of bone fractures. To reduce fracture incidence requires both prevention of falls and maintenance of bone strength.PubMed searches were performed, for studies of the epidemiology of fractures, bone physiology, endocrine effects, osteoporosis measurement, genetics, prevention and effectiveness. Topic summaries were presented to the Workshop Group and omissions or disagreements were resolved by discussion.Ageing ...

  14. Pelvic Insufficiency Fractures

    OpenAIRE

    O’Connor, Timothy J.; Cole, Peter A.

    2014-01-01

    Pelvic insufficiency fractures may occur in the absence of trauma or as a result of low-energy trauma in osteoporotic bone. With a growing geriatric population, the incidence of pelvic insufficiency fracture has increased over the last 3 decades and will continue to do so. These fractures can cause considerable pain, loss of independence, and economic burden to both the patient and the health care system. While many of these injuries are identified and treated based on plain radiographs, some...

  15. Fracture Nasal Bone

    OpenAIRE

    Balasubramanian, Thiagarajan; Venkatesan, Ulaganathan

    2013-01-01

    Nose is the most prominent part of the face, hence it is likely to be the most common structure to be injured in the face. Although fractures involving the nasal bones are very common, it is often ignored by the patient. Patients with fractures of nasal bone will have deformity, tenderness, haemorrhage, edema, ecchymosis, instability, and crepitation. These features may be present in varying combinations. This article discusses the pathophysiology of these fractures, role of radiography and u...

  16. FRACTURE NASAL BONES

    OpenAIRE

    Balasubramanian Thaigarajan; Venkatesan Ulaganathan

    2013-01-01

    Nose is the most prominent part of the face, hence it is likely to be the most common structure to be injured in the face. Although fractures involving the nasal bones are very common, it is often ignored by the patient. Patients with fractures of nasal bone will have deformity, tenderness, haemorrhage, edema, ecchymosis, instability, and crepitation. These features may be present in varying combinations. This article discusses the pathophysiology of these fractures, role of radiography a...

  17. Fracture mechanics behavior of the T91 martensitic steel in contact with liquid lead-bismuth eutectic for application in an accelerator driven system

    Energy Technology Data Exchange (ETDEWEB)

    Auger, T., E-mail: thierry.auger@ecp.fr [CNRS-MSSMAT, Ecole Centrale Paris, Grande Voie des Vignes, 92290 Chatenay-Malabry Cedex (France); Gorse, D. [CNRS-LSI, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Hamouche-Hadjem, Z. [CNAM, 2 rue Conte, 75003 Paris (France); Van den Bosch, J.; Coen, G.; Almazouzi, A. [SCK-CEN (Belgian Nuclear Research Centre), Boeretang 200, 2400 Mol (Belgium); Hojna, A.; Dalikova, K.; Di Gabriele, F. [Ustav Jaderneho Vyzkumu Rez a.s., Rez 130, Husinec 25068 (Czech Republic); Serrano, M. [CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Gessi, A.; Agostini, P. [ENEA, CR Brasimone 40032 Camugnano, Bologna (Italy); Vogt, J.-B.; Serre, I. [CNRS-LMPGM, 59655 Villeneuved' Ascq Cedex (France)

    2011-08-31

    The fracture toughness of the T91 martensitic steel in liquid lead-bismuth eutectic has been measured at 300 deg. C in plane stress and plane strain conditions. The effect of achieving wetting at the crack tip prior starting mechanical testing is demonstrated to be the key factor for a correct evaluation of the potential effect of LBE on fracture toughness. In plane stress, one observes a serrated fracture mode associated with a reduction of fracture toughness between 20% and 30%. The toughness reduction is higher in plane strain where the cleavage fracture mode prevails. The difference between the two fracture modes is due to the higher plastic deformation level reached at final fracture in plane stress and to the higher crack growth rate in plane strain. These results will be useful for the design of future nuclear systems cooled by LBE planning to use martensitic steels as structural materials.

  18. Increasing fracture during childhood

    International Nuclear Information System (INIS)

    Although calvarial fractures usually heal well in children, it may occur that interposition of dura and arachnoidea leads to an enlargement of the fracture line, and to formation of a leptomeningeal cyst accompanied by an arrosion of the bone. This defect of the skull cap is the so-called 'growing fracture of the vault of the cranium'. Clinical manifestation of this growing fracture is a swelling that occurs after some weeks on the skull. Diagnostic evaluation can be done by CT and X-ray radiography. (orig./GDG)

  19. Sequence specificity of DNA cleavage by Micrococcus luteus γ endonuclease

    International Nuclear Information System (INIS)

    DNA fragments of defined sequence have been used to determine the sites of cleavage by γ-endonuclease activity in extracts prepared from Micrococcus luteus. End-labeled DNA restriction fragments of pBR322 DNA that had been irradiated under nitrogen in the presence of potassium iodide or t-butanol were treated with M. luteus γ endonuclease and analyzed on irradiated DNA preferentially at the positions of cytosines and thymines. DNA cleavage occurred immediately to the 3' side of pyrimidines in irradiated DNA and resulted in fragments that terminate in a 5'-phosphoryl group. These studies indicate that both altered cytosines and thymines may be important DNA lesions requiring repair after exposure to γ radiation

  20. Mutagenesis of the yellow fever virus NS2B/3 cleavage site: determinants of cleavage site specificity and effects on polyprotein processing and viral replication.

    OpenAIRE

    Chambers, T J; Nestorowicz, A.; Rice, C.M.

    1995-01-01

    The determinants of cleavage site specificity of the yellow fever virus (YF) NS3 proteinase for its 2B/3 cleavage site have been studied by using site-directed mutagenesis. Mutations at residues within the GARR decreases S sequence were tested for effects on cis cleavage of an NS2B-3(181) polyprotein during cell-free translation. At the P1 position, only the conservative substitution R-->K exhibited significant levels of cleavage. Conservative and nonconservative substitutions were tolerated ...

  1. Fracture of the styloid process associated with the mandible fracture

    OpenAIRE

    K N Dubey; Ajay Bajaj; Ish Kumar

    2013-01-01

    Fracture of the styloid process (SP) of temporal bone is an uncommon injuries. Fracture of the SP can be associated with the facial injuries including mandible fracture. However, injury to the SP may be concealed and missed diagnosis may lead to the improper or various unnecessary treatments. A rare case of SP fracture associated with the ipsilateral mandibular fracture and also the diagnostic and management considerations of the SP fracture are discussed.

  2. Fracture of the styloid process associated with the mandible fracture

    Directory of Open Access Journals (Sweden)

    K N Dubey

    2013-01-01

    Full Text Available Fracture of the styloid process (SP of temporal bone is an uncommon injuries. Fracture of the SP can be associated with the facial injuries including mandible fracture. However, injury to the SP may be concealed and missed diagnosis may lead to the improper or various unnecessary treatments. A rare case of SP fracture associated with the ipsilateral mandibular fracture and also the diagnostic and management considerations of the SP fracture are discussed.

  3. Small Molecule-Mediated Cleavage of RNA in Living Cells

    OpenAIRE

    Guan, Lirui; Disney, Matthew D.

    2012-01-01

    Antisense oligonucleotides and small interfering RNAs (siRNAs) control gene expression by triggering the degradation of a mRNA via recruitment of RNase H or the RNA-induced silencing complex (RISC), respectively.[1] These approaches are hampered, however, by the poor cellular permeability of oligonucleotides. A small molecule approach to cleave RNA targets could obviate uptake issues. Several compounds can induce RNA cleavage in vitro,[2] however, to the best of our knowledge no small molecul...

  4. Effects of Cysteamine on Sheep Embryo Cleavage Rates

    OpenAIRE

    ENGİNLER, Sinem Ö; ÖZDAŞ, Özen B.; SANDAL, Asiye İ.; ARICI, Ramazan; GÜNDÜZ, Mehmet C.; BARAN, Alper; TEK, Çağatay; KILIÇARSLAN, Mehmet R.; Ak, Kemal

    2015-01-01

    Oxidative stress during in vitro culture leads to defects in development of gametes and embryos. Several antioxidants such as cysteamine, L-ascorbic acid, beta mercaptoethanol, cysteine, glutathione, proteins, vitamins have been used to supplement culture media to counter the oxidative stress. This study was conducted to detect the effect of adding cysteamine to the maturation medium to subsequent cleavage rates of sheep embryos. Totally 604 ovaries were obtained by ten replica and 2060 oocyt...

  5. Fe-Catalyzed Oxidative Cleavage of Unsaturated Fatty Acids

    OpenAIRE

    Spannring, P.

    2013-01-01

    The oxidative cleavage of unsaturated fatty acids into aldehydes or carboxylic acids gives access to valuable products. The products can be used as chemical building blocks, as emulsifiers or in the paint or polymer industry. Ozonolysis is applied industrially to cleave the fatty acid oleic acid into the aldehydes nonanal and 9-oxo-nonanoic acid or into pelargonic and azelaic acid. Considerable hazards, including explosion risks, are associated with the use of ozone, and alternative processes...

  6. Developing a programmed restriction endonuclease for highly specific DNA cleavage

    OpenAIRE

    Eisenschmidt, Kristin; Lanio, Thomas; Simoncsits, András; Jeltsch, Albert; Pingoud, Vera; Wende, Wolfgang; Pingoud, Alfred

    2005-01-01

    Specific cleavage of large DNA molecules at few sites, necessary for the analysis of genomic DNA or for targeting individual genes in complex genomes, requires endonucleases of extremely high specificity. Restriction endonucleases (REase) that recognize DNA sequences of 4–8 bp are not sufficiently specific for this purpose. In principle, the specificity of REases can be extended by fusion to sequence recognition modules, e.g. specific DNA-binding domains or triple-helix forming oligonucleotid...

  7. The pattern of DNA cleavage intensity around indels

    OpenAIRE

    Wei Chen; Liqing Zhang

    2015-01-01

    Indels (insertions and deletions) are the second most common form of genetic variations in the eukaryotic genomes and are responsible for a multitude of genetic diseases. Despite its significance, detailed molecular mechanisms for indel generation are still unclear. Here we examined 2,656,597 small human and mouse germline indels, 16,742 human somatic indels, 10,599 large human insertions, and 5,822 large chimpanzee insertions and systematically analyzed the patterns of DNA cleavage intensiti...

  8. Mycothiol synthesis by an anomerization reaction through endocyclic cleavage

    Science.gov (United States)

    2016-01-01

    Summary Mycothiol is found in Gram-positive bacteria, where it helps in maintaining a reducing intracellular environment and it plays an important role in protecting the cell from toxic chemicals. The inhibition of the mycothiol biosynthesis is considered as a treatment for tuberculosis. Mycothiol contains an α-aminoglycoside, which is difficult to prepare stereoselectively by a conventional glycosylation reaction. In this study, mycothiol was synthesized by an anomerization reaction from an easily prepared β-aminoglycoside through endocyclic cleavage. PMID:26977192

  9. Centrocortin Cooperates with Centrosomin to Organize Drosophila Embryonic Cleavage Furrows

    OpenAIRE

    Kao, Ling-Rong; Timothy L Megraw

    2009-01-01

    In the Drosophila early embryo the centrosome coordinates assembly of cleavage furrows [1–3]. Currently, the molecular pathway that links the centrosome and the cortical microfilaments is unknown. In centrosomin (cnn) mutants, where the centriole forms but the centrosome pericentriolar material (PCM) fails to assemble [4, 5], actin microfilaments are not organized into furrows at the syncytial cortex [6]. While CNN is required for centrosome assembly and function [4, 6, 7], little is known of...

  10. Embryo apoptosis identification: Oocyte grade or cleavage stage?

    OpenAIRE

    Bakri, Noraina Mohd; Ibrahim, Siti Fatimah; Osman, Nurul Atikah; Hasan, Nurhaslina; Jaffar, Farah Hanan Fathihah; Rahman, Zulaiha Abdul; Osman, Khairul

    2015-01-01

    Apoptosis is a programed cell death that is vital for tissue homeostasis. However, embryo apoptosis had been known to be related to embryo fragmentation which should be avoided in in vitro fertilization (IVF). The purpose of this study was to evaluate the relationship of embryo apoptosis with the grade of immature oocytes and cleavage stage of in vitro produced (IVP) cattle embryos. This study consisted of 345 oocytes collected through ovary slicing. Immature oocytes were graded as A, B and C...

  11. DNAzyme-Controlled Cleavage of Dimer and Trimer Origami Tiles.

    Science.gov (United States)

    Wu, Na; Willner, Itamar

    2016-04-13

    Dimers of origami tiles are bridged by the Pb(2+)-dependent DNAzyme sequence and its substrate or by the histidine-dependent DNAzyme sequence and its substrate to yield the dimers T1-T2 and T3-T4, respectively. The dimers are cleaved to monomer tiles in the presence of Pb(2+)-ions or histidine as triggers. Similarly, trimers of origami tiles are constructed by bridging the tiles with the Pb(2+)-ion-dependent DNAzyme sequence and the histidine-dependent DNAzyme sequence and their substrates yielding the trimer T1-T5-T4. In the presence of Pb(2+)-ions and/or histidine as triggers, the programmed cleavage of trimer proceeds. Using Pb(2+) or histidine as trigger cleaves the trimer to yield T5-T4 and T1 or the dimer T1-T5 and T4, respectively. In the presence of Pb(2+)-ions and histidine as triggers, the cleavage products are the monomer tiles T1, T5, and T4. The different cleavage products are identified by labeling the tiles with 0, 1, or 2 streptavidin labels and AFM imaging. PMID:26931508

  12. Cleavage mechanoluminescence in elemental and III-V semiconductors

    CERN Document Server

    Chandra, B P; Gour, A S; Chandra, V K; Gupta, R K

    2003-01-01

    The present paper reports the theory of mechanoluminescence (ML) produced during cleavage of elemental and III-V semiconductors. It seems that the formation of crack-induced localized states is responsible for the ML excitation produced during the cleavage of elemental and III-V semiconductors. According to this mechanism, as the atoms are drawn away from each other in an advancing crack tip, the decreasing wave function overlap across the crack may result in localized states which is associated with increasing electron energy. If the energy of these localized states approach that of the conduction band, transition to the conduction band via tunnelling would be possible, creating minority carriers, and consequently the electron-hole recombination may give rise to mechanoluminescence. When an elemental or III-V semiconductor is cleaved, initially the ML intensity increases with time, attains a peak value I sub m at the time t sub m corresponding to completion of the cleavage of the semiconductor, and then it d...

  13. Mechanism of metabolic cleavage of a furan ring

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, T.; Sugihara, J.; Harigaya, S.

    1987-11-01

    We studied the mechanism of metabolic cleavage of a furan ring, using a new hypolipidemic agent, ethyl 2-(4-chlorophenyl)-5-(2-furyl)oxazole-4-acetate (TA-1801), as a model compound. A TA-1801 analogue labeled with deuterium at the 5-position of its furan ring was administered orally to rats. The analysis of urinary metabolites by GC/MS revealed that the deuterium of the furan was retained in the ring-opened metabolite (M3). Metabolic cleavage of furan has been generally considered to proceed by hydroxylation of the 5-position followed by tautomerism and hydrolysis of the resulting 5-hydroxyfuran derivative. However, if the cleavage proceeded by this pathway, the deuterium of the 5-position would be eliminated during hydroxylation. Therefore, we propose that the ring was cleaved directly to form an unsaturated aldehyde, considering the mechanism of oxidation by cytochrome P-450. Although this intermediate was not detected in the biological specimens, a synthetic unsaturated aldehyde was transformed to the actual urinary metabolites M2 and M3 (major ring-opened metabolites) in the isolated rat liver.

  14. Mechanism of metabolic cleavage of a furan ring

    International Nuclear Information System (INIS)

    We studied the mechanism of metabolic cleavage of a furan ring, using a new hypolipidemic agent, ethyl 2-(4-chlorophenyl)-5-(2-furyl)oxazole-4-acetate (TA-1801), as a model compound. A TA-1801 analogue labeled with deuterium at the 5-position of its furan ring was administered orally to rats. The analysis of urinary metabolites by GC/MS revealed that the deuterium of the furan was retained in the ring-opened metabolite (M3). Metabolic cleavage of furan has been generally considered to proceed by hydroxylation of the 5-position followed by tautomerism and hydrolysis of the resulting 5-hydroxyfuran derivative. However, if the cleavage proceeded by this pathway, the deuterium of the 5-position would be eliminated during hydroxylation. Therefore, we propose that the ring was cleaved directly to form an unsaturated aldehyde, considering the mechanism of oxidation by cytochrome P-450. Although this intermediate was not detected in the biological specimens, a synthetic unsaturated aldehyde was transformed to the actual urinary metabolites M2 and M3 (major ring-opened metabolites) in the isolated rat liver

  15. Cleavage mechanoluminescence in elemental and III-V semiconductors

    International Nuclear Information System (INIS)

    The present paper reports the theory of mechanoluminescence (ML) produced during cleavage of elemental and III-V semiconductors. It seems that the formation of crack-induced localized states is responsible for the ML excitation produced during the cleavage of elemental and III-V semiconductors. According to this mechanism, as the atoms are drawn away from each other in an advancing crack tip, the decreasing wave function overlap across the crack may result in localized states which is associated with increasing electron energy. If the energy of these localized states approach that of the conduction band, transition to the conduction band via tunnelling would be possible, creating minority carriers, and consequently the electron-hole recombination may give rise to mechanoluminescence. When an elemental or III-V semiconductor is cleaved, initially the ML intensity increases with time, attains a peak value Im at the time tm corresponding to completion of the cleavage of the semiconductor, and then it decreases following power law decay. Expressions are derived for the ML intensity Im corresponding to the peak of the ML intensity versus time curve and for the total ML intensity IT. It is shown that both Im and IT should increase directly with the area of the newly created surfaces of the crystals. From the measurements of the ML intensity, the velocity of crack propagation in material can be determined by using the relation v=H/tm

  16. Demethylation and cleavage of dimethylsulfoniopropionate in marine intertidal sediments

    Science.gov (United States)

    Visscher, P.T.; Kiene, R.P.; Taylor, B.F.

    1994-01-01

    Demethylation and cleavage of dimethylsulfoniopropionate (DMSP) was measured in three different types of,intertidal marine sediments: a cyanobacterial mat, a diatom-covered tidal flat and a carbonate sediment. Consumption rates of added DMSP were highest in cyanobacterial mat slurries (59 ?? mol DMSP l-1 slurry h-1) and lower in slurries from a diatom mat and a carbonate tidal sediment (24 and 9 ??mol DMSP l-1 h-1, respectively). Dimethyl sulfide (DMS) and 3-mercaptopropionate (MPA) were produced simultaneously during DMSP consumption, indicating that cleavage and demethylation occurred at the same time. Viable counts of DMSP-utilizing bacteria revealed a population of 2 x 107 cells cm-3 sediment (90% of these cleaved DMSP to DMS, 10% demethylated DMSP to MPA) in the cyanobacterial mat, 7 x 105 cells cm-3 in the diatom mat (23% cleavers, 77% demethylators), and 9 x 104 cells cm-3 (20% cleavers and 80% demethylators) in the carbonate sediment. In slurries of the diatom mat, the rate of MPA production from added 3-methiolpropionate (MMPA) was 50% of the rate of MPA formation from DMSP. The presence of a large population of demethylating bacteria and the production of MPA from DMSP suggest that the demethylation pathway, in addition to cleavage, contributes significantly to DMSP consumption in coastal sediments.

  17. Hyperphosphorylation and cleavage at D421 enhance tau secretion.

    Directory of Open Access Journals (Sweden)

    Vanessa Plouffe

    Full Text Available It is well established that tau pathology propagates in a predictable manner in Alzheimer's disease (AD. Moreover, tau accumulates in the cerebrospinal fluid (CSF of AD's patients. The mechanisms underlying the propagation of tau pathology and its accumulation in the CSF remain to be elucidated. Recent studies have reported that human tau was secreted by neurons and non-neuronal cells when it was overexpressed indicating that tau secretion could contribute to the spreading of tau pathology in the brain and could lead to its accumulation in the CSF. In the present study, we showed that the overexpression of human tau resulted in its secretion by Hela cells. The main form of tau secreted by these cells was cleaved at the C-terminal. Surprisingly, secreted tau was dephosphorylated at several sites in comparison to intracellular tau which presented a strong immunoreactivity to all phospho-dependent antibodies tested. Our data also revealed that phosphorylation and cleavage of tau favored its secretion by Hela cells. Indeed, the mimicking of phosphorylation at 12 sites known to be phosphorylated in AD enhanced tau secretion. A mutant form of tau truncated at D421, the preferential cleavage site of caspase-3, was also significantly more secreted than wild-type tau. Taken together, our results indicate that hyperphosphorylation and cleavage of tau by favoring its secretion could contribute to the propagation of tau pathology in the brain and its accumulation in the CSF.

  18. Regioselective Cleavage of Thioether Linkages in Microcystin Conjugates.

    Science.gov (United States)

    Zemskov, Ivan; Kropp, Heike M; Wittmann, Valentin

    2016-07-25

    Microcystins are cyanobacterial toxins that can be found in fresh and coastal waters during algal blooms. Microcystin contamination of water can cause severe poisoning of animals and humans. Quantification of these toxins in biological samples is complicated because a major proportion of microcystins is covalently linked to proteins through thioether bonds formed through a Michael-type addition of cysteine residues of proteins to an N-methyldehydroalanine residue in the microcystins. We investigated chemical methods that can be used to cleave such thioether bonds by means of an elimination reaction that leaves the microcystin backbone intact for subsequent analysis. The known reagent O-mesitylenesulfonylhydroxylamine (MSH) led to regioselective thioether cleavage, but a large excess of reagent was needed, thus making purification challenging. An unexpected side reaction observed during the investigation of the base-induced elimination inspired us to develop a new thioether-cleavage methodology based on the addition of propargylamine as a nucleophile that can trap the elimination product. This methodology could be successfully applied to the quantitative cleavage of a microcystin-LF-glutathione conjugate. The alkyne moiety introduced by this procedure offers the possibility for further reactions with azides by using click chemistry, which might be useful for the derivatization or isolation of microcystins. PMID:27346324

  19. Sequence specificity of DNA cleavage by Micrococcus luteus gamma endonuclease

    International Nuclear Information System (INIS)

    Gamma irradiation induces the formation of lesions in DNA that are cleaved by an endonuclease activity in Micrococcus luteus extract. DNA fragments of defined sequence an DNA sequencing techniques were used to determine the sites of cleavage by this activity. /sup 32/P end-labelled DNA restriction fragments were gamma irradiated under N/sub 2/ and in the presence of KI (conditions which maximize the enzyme sensitive site to strand break ratio), treated with M. luteus extract, and analyzed by electrophoresis on denaturing polyacrylamide gels. Irradiated DNA was preferentially cleaved by the extract at sites of cytosine and thymine. Little or no cleavage was observed at purines. Scission of 3' end-labelled DNA at altered pyrimidines resulted in fragments that had electrophoretic mobilities similar to those of DNA fragments that were phosphorylated at the 5' terminus. The presence of a 5' phosphate was confirmed by a change in electrophoretic mobility after phosphatase treatment of the fragments. The sites of endonucleolytic cleavage by M. luteus extract were compared to those of the purified Escherichia coli endonuclease III, which has been shown to be active against x-irradiated DNA. Preliminary results from velocity sedimentation studies indicate that these two enzyme preparations differ in specificity

  20. Microstructure and fracture behavior of F82H steel under different irradiation and tensile test conditions

    Science.gov (United States)

    Wang, K.; Dai, Y.; Spätig, P.

    2016-01-01

    Specimens of martensitic steel F82H were irradiated to doses ranging from 10.7 dpa/850 appm He to 19.6 dpa/1740 appm He at temperatures between 165 and 305 °C in the second experiment of SINQ Target Irradiation Program (STIP-II). Tensile tests were conducted at different temperatures and various fracture modes were observed. Microstructural changes including irradiation-induced defect clusters, dislocation loops and helium bubbles under different irradiation conditions were investigated using transmission electron microscopy (TEM). The deformation microstructures of tensile tested specimens were carefully examined to understand the underlying deformation mechanisms. Deformation twinning was for the first time observed in irradiated martensitic steels. A change of deformation mechanism from dislocation channeling to deformation twinning was observed when the fracture mode changed from rather ductile (quasi-cleavage) to brittle (intergranular or cleavage and intergranular mixed).

  1. The influence of environment on the formation of fluting microstructures during fracture of zircaloy

    International Nuclear Information System (INIS)

    Fluting microstructures are commonly-occurring features on Zircaloy fractures produced under stress-corrosion cracking (SCC) and liquid (or solid) metal embrittlement (LME) conditions and they are generally closely associated with areas of cleavage cracking. Although it is widely believed that flutings are a consequence of localised plastic deformation near the cleavage cracks and that the aggressive chemical agents do not contribute directly to fluting formation there is little clear experimental evidence to support that view. Consequently the small programme of tests, described here, was performed in order to ascertain whether flutings can be generated in Zircaloy during exposure to stress in the absence of a SCC or LME agent. The implications of the results are discussed in terms of the currently proposed mechanisms for fluting formation in particular, and crack propagation generally, in Zircaloy SCC fracture. (orig.)

  2. Hip Fractures among Older Adults

    Science.gov (United States)

    ... online training for health care providers. Learn More Hip Fractures Among Older Adults Recommend on Facebook Tweet ... get older. What You Can Do to Prevent Hip Fractures You can prevent hip fractures by taking ...

  3. Concrete fracture models and applications

    CERN Document Server

    Kumar, Shailendra

    2011-01-01

    Concrete-Fracture Models and Applications provides a basic introduction to nonlinear concrete fracture models. Readers will find a state-of-the-art review on various aspects of the material behavior and development of different concrete fracture models.

  4. Cleavage dynamic propagation analysis in a nuclear reactor pressure vessel steel using a high-speed camera

    International Nuclear Information System (INIS)

    Initiation stage of cracks is considered as a key issue, but more and more component integrity analyses investigate the crack propagation and arrest possibility. This study deals with physical mechanisms of cleavage crack propagation and numerical computations related to brittle fracture. Dynamic effects, involved in unstable cleavage crack propagation, have to be taken into account to properly depict brittle crack propagation, arrest and possible propagation re-initiation events. Experiments were carried out on thin CT specimens made of 16MND5 PWR vessel steel at five temperatures (-150 degrees C, -125 degrees C, -100 degrees C, -75 degrees C, -50 degrees C). In addition to standard crack gages, an innovative experimental technique has been used to determine crack propagation. By the means of developments on the experimental protocol (improvements of isolation and airtightness of the thermal chamber, optimization of the experimental protocol to eliminate ice in the thermal chamber and in order to have a good acquisition quality), use of a high speed framing camera was made possible to measure crack propagation on a CT mirror polished surface. This optical device, combined with this optimized experimental process, has allowed the study of straight and branching crack paths with high accuracy. The framing camera (520 000 fps up to 1 100 000 fps) has allowed to have a very accurate estimation of crack speed even up to 1000 m.s-1 and also to detect some phases of crack branching during propagation and phases of arrest-re-initiation. Numerical computations, based on X-FEM and combining a local non linear dynamic approach with a RKR type fracture stress criterion, have been performed to depict experimental crack behavior. This paper describes this innovative experimentation and the interpretation by FE calculations and SEM observations associated with quantitative 3D optical microscopy. (authors)

  5. Recommendations for the application of fracture toughness data for structural integrity assessments

    International Nuclear Information System (INIS)

    Large scale testing for the purpose of fracture mechanics verification is essentially directed towards the validation of the transferability of material data obtained with small specimens. Unfortunately the results are sometimes controversial, insinuating that the transferability is imprecise at the very least. However, it seems that in many cases the controversy is due to an improper application of the small specimen data. Present testing standards do not give any recommendations for the correct application of fracture toughness data and yet this is a crucial point for successful structural integrity assessment and fracture mechanics verification. In this presentation the topic concerning recommendations is addressed, focusing on the application of brittle (cleavage type) fracture data. Simple guidelines for obtaining optimum open-quotes best-close quotes and open-quotes safe-close quotes estimates of the behavior of the actual structure based on small specimen data are presented. 51 refs., 16 figs., 1 tab

  6. Degradation of impact fracture during accelerated aging of weld metal on microalloyed steel

    International Nuclear Information System (INIS)

    The effect of accelerated aging on the toughness and fracture of the longitudinal weld metal on an API5L-X52 line pipe steel was evaluated by Charpy V-notch impact test, fracture analysis and transmission electron microscopy. Aging was performed at 250 degree centigrade for 100 to 1000 h. The impact results indicated a significant reduction in the fracture energy and impact toughness as a function of aging time, which were achieved by the scanning electron microscope fractography that showed a decrease in the vol fraction of microvoids by Charpy ductile failure with the aging time, which favored the brittle fracture by transgranular cleavage. The minimum vol fraction of microvoids was reached at 500 h due to the peak aged. The microstructural analysis indicated the precipitation of transgranular iron nano carbides in the aged specimens, which was related to the deterioration of toughness and change in the ductile to brittle behavior. (Author) 15 refs

  7. Review of penile fracture

    International Nuclear Information System (INIS)

    A detailed current review was performed of penile fracture. A literature search and analysis were compiled of studies made in the last 15 years about the proper management of penile fracture. These have allowed for a practical guide to the diagnosis and early treatment by the urologist

  8. THORACIC SPINE FRACTURES

    Institute of Scientific and Technical Information of China (English)

    戴力扬

    2001-01-01

    Objective. To investigate the unique characteristics and treatment of thoracic spine fractures.Methods. Severty-seven patients with thoracic spine fractures were retrospectively reviewed. Of these, therewere 37 compressior fractures, 34 fracture-dislocations, 3 burst fractures and 3 burst-dislocations. Twenty-six pa-tients had a complete lesion of the spinal cord, 14 sustained a neurologically incomplete injury, and 37 wereneurologically intact. Fifty-three patients were treated nonoperatively and 24 treated operatively.Results. All patients were followed up for 2 ~ 15 years. None of the 26 patients with a complete lesion recov-ered any significant function. Of 37 neurologically intact patients, 13 had local pain although all of them re-mained normal function. Two of 14 patients with incomplete paraplegia returned to normal, 7 recovered some func-tion and 5 did not recovered.Conclusions. E ecause of the unique anatomy and biomechanics of the thoracic spine, the classification common-ly applied to thoracolumbar fractures is not suitable for thoracic fractures. Fusion and instrumentation are indicat-ed when the fractures are unstable, while patients with incomplete lesion of the spinal cord may be the candidatesfor supplemented decompression.

  9. Pediatric Thighbone (Femur) Fracture

    Science.gov (United States)

    ... carefully examine the leg, including the hip and knee. A child with a thighbone fracture should always be evaluated for other serious injuries. ... down the uninjured leg, or stop at the knee or hip. Your doctor will decide ... your child’s fracture. Your doctor will sedate your child for the ...

  10. Vertebral Fracture Prediction

    DEFF Research Database (Denmark)

    2008-01-01

    Vertebral Fracture Prediction A method of processing data derived from an image of at least part of a spine is provided for estimating the risk of a future fracture in vertebraeof the spine. Position data relating to at least four neighbouring vertebrae of the spine is processed. The curvature of...

  11. Tibia (Shinbone) Shaft Fractures

    Science.gov (United States)

    ... the recovery period. For example, if so tissue injury is present with a fracture, the knee, ankle, foot, and toes may be mobilized early in ... bone are typically the result of higher energy mechanisms (as opposed to the spiral-type fractures ... injuries). They also have increased injury to the tissues ...

  12. Proximal femoral fractures

    DEFF Research Database (Denmark)

    Palm, Henrik; Teixidor, Jordi

    2015-01-01

    guidelines for hip fracture surgery and discuss a method for future pathway/guideline implementation and evaluation. METHODS: By a PubMed search in March 2015 six studies of surgical treatment pathways covering all types of proximal femoral fractures with publication after 1995 were identified. Also we......BACKGROUND: In hip fracture surgery, the exact choice of implant often remains somewhat unclear for the individual surgeon, but the growing literature consensus has enabled publication of evidence-based surgical treatment pathways. The aim of this article was to review author pathways and national......-displaced femoral neck fractures and prosthesis for displaced among the elderly; and sliding hip screw for stabile- and intramedullary nails for unstable- and sub-trochanteric fractures) but they are based on a variety of criteria and definitions - and often leave wide space for the individual surgeons' subjective...

  13. Apparent capitellar fractures.

    Science.gov (United States)

    Ring, David

    2007-11-01

    Isolated capitellar fractures are rare but are identified as such, even when they are more complex, because the displaced capitellar fracture is usually the most obvious and identifiable radiographic finding and because teaching has traditionally underemphasized the involvement of the trochlea in such fractures. The author prefers the term 'apparent capitellar fractures' and draws on his experience to explain why he favors three-dimensional CT for depicting fracture detail. This article discusses treatment options, emphasizing open reduction and internal fixation to restore the native elbow. Operative techniques, including extensile lateral exposure and olecranon osteotomy; fixation techniques; and elbow arthroplasty, are described. Complications, such as ulnar neuropathy and infection, are also covered. PMID:18054674

  14. Probabilistic fracture mechanics

    International Nuclear Information System (INIS)

    It has been attempted to present the elements of probabilistic fracture mechanics in a self-contained way. First, for brittle fracture, damage theories are discussed which allow for the effects of both size and local strength of the structure on the probability of fracture. Second, combined crack and damage theories are presented. They provide insight into macro-crack formation and take into account the effects of crack orientation and multiaxial states of stress. For fatigue, both the two-phase theory of damage and crack extension as well as the cumulative theory (of damage or of crack extension) are presented. They give estimates for the lifetime of a structure under random load. The effect of random material properties may be included. Finally, an assessment of the probability of failure of reactor pressure vessels is discussed. There, brittle fracture and fatigue are taken into account and both fracture toughness and crack size are considered to be random quantities. (Auth.)

  15. FALSIRE phase 2: CSNI project for fracture analyses of large- scale international reference experiments

    International Nuclear Information System (INIS)

    A summary of Phase II of the Project for Fracture Analysis of Large-Scale International Reference Experiments (FALSIRE) is presented. FALSIRE I was initiated by the CSNI/FAG in 1988 to assess various fracture methodologies through interpretive analyses of six large-scale fracture experiments. Following the successful completion of FALSIRE I in 1992, several participating organizations indicated a desire to proceed with further evaluation of fracture analysis methods in a Phase II program. FALSIRE II included seven reference cleavage fracture experiments that focused primarily on behavior of relatively shallow cracks in the transition temperature region. Included were experiments for which cracks showed either unstable extension or two stages of extension (e.g., stable crack extension followed by unstable extension) under transient thermal and mechanical loadings. Also, crack initiation was investigated in connection with clad surfaces and with biaxial loading conditions. A comparative assessment and discussion of the analysis results are presented in the report. Generally, structural responses of the test specimens were predicted with tolerable scatter bands; these represent a marked improvement over the results achieved in the initial phase (FALSIRE I). The analyses revealed that the loss-of-constraint effects observed in specific cases require a second (or dual) fracture parameter to be introduced into the fracture model to characterize crack-tip conditions. Additional toughness data obtained from a range of specimen geometries and constraint conditions are required to validate these dual-parameter cleavage fracture methodologies. Finally, proposals for future work in the context of cooperative international analytical projects similar to FALSIRE are provided

  16. The use of ion channeling and elastic recoil detection in determining the mechanism of cleavage in the ion-cut process

    International Nuclear Information System (INIS)

    Hydrogen ion implantation in Si has been shown to be an effective means of inducing cleavage in Si and facilitating the transfer of thin slices to other substrates, a process known as ion-cut. In our experiments silicon wafers were implanted with 40 keV protons to a variety of ion doses ranging from 5x1016 to 1x1017 cm-2 and subsequently annealed at 600 deg. C. Under all of these conditions ion-cutting in the form of 'popping off' discrete blisters was obtained. The cleavage mechanisms in these samples were studied through the combined use of Rutherford backscattering spectroscopy in channeling mode, elastic recoil detection analysis, and scanning electron microscopy. Our analyses had shown that the cleavage location in Si is largely controlled by the lattice damage that is generated by the H-implantation process. At lower H doses, the cut location is well correlated with the damage peak and can be explained by damage-induced in-plane stress and the corresponding out-of-plane strain. However, at higher implantation doses the ion-cut location shifts to a portion of the crystal which contains lower damage and sufficient concentration of H. This effect can be explained by the changing fracture mechanics at high H concentrations in heavily damaged Si

  17. Radiological diagnosis of fractures

    International Nuclear Information System (INIS)

    This book is about radiology of fractures. While it contains sections of clinical features it is not intended that readers should rely entirely upon these for the diagnosis and management of the injured patient. As in the diagnosis and treatment of all medical problems, fracture management must be carried out in a logical step-by-step fashion - namely, history, examination, investigation, differential diagnosis, diagnosis and then treatment. Each section deals with a specific anatomical area and begins with line drawings of the normal radiographs demonstrating the anatomy. Accessory views that may be requested, and the indications for these, are included. Any radiological pitfalls for the area in general are then described. The fractures in adults are then examined in turn, their radiological features described, and any pitfalls in their diagnosis discussed. A brief note of important clinical findings is included. A brief mention is made of pediatric fractures which are of significance and their differences to the adult pattern indicated. Although fractures can be classified into types with different characteristics, in life every fracture is individual. Fractures by and large follow common patterns, but many have variations

  18. Inverse fracture network modelling

    International Nuclear Information System (INIS)

    The basic problem in analyzing flow and transport in fractured rock is that the flow may be largely governed by a poorly connected network of fractures. Flow in such a system cannot be modeled with traditional modelling techniques. Fracture network models also have a limitation, in that they are based on geological data on fracture geometry even though it is known that only a small portion of fractures observed is hydraulically active. This paper discusses a new technique developed for treating the problem as well as presents a modelling example carried out to apply it. The approach is developed in Lawrence Berkeley Laboratory and it treats the fracture zone as an 'equivalent discontinuum'. The discontinuous nature of the problem is represented through flow on a partially filled lattice. An equivalent discontinuum model is constructed by adding and removing conductive elements through a statistical inverse technique called 'simulated annealing'. The fracture network model is 'annealed' until the modified systems behaves like the observed. The further development of the approach continues at LBL and in a joint LBL/VTT collaboration project the possibilities to apply the technique in Finnish conditions are investigated

  19. FRACTURE NASAL BONES

    Directory of Open Access Journals (Sweden)

    Balasubramanian Thaigarajan

    2013-03-01

    Full Text Available Nose is the most prominent part of the face, hence it is likely to be the most common structure to be injured in the face. Although fractures involving the nasal bones are very common, it is often ignored by the patient. Patients with fractures of nasal bone will have deformity, tenderness, haemorrhage, edema, ecchymosis, instability, and crepitation. These features may be present in varying combinations. This article discusses the pathophysiology of these fractures, role of radiography and ultrasound in their diagnosis and their management.

  20. Copper-dependent cleavage of DNA of bleomycin

    International Nuclear Information System (INIS)

    DNA strand scission by bleomycin in the presence of Cu and Fe was further characterized. It was found that DNA degradation occurred readily upon admixture of Cu(I) or Cu(II) + dithiothreitol + bleomycin, but only where the order of addition precluded initial formation of Cu(II)-bleomycin or where sufficient time was permitted for reduction of formed Cu(II)-bleomycin to Cu(I)-bleomycin. DNA strand scission mediated by Cu + dithiothreitol + bleomycin was inhibited by the copper-selective agent bathocuproine when the experiment was carried out under conditions consistent with Cu chelation by bathocuproine on the time scale of the experiment. Remarkably, it was found that the extent of DNA degradation obtained with bleomycin in the presence of Fe and Cu was greater than that obtained with either metal ion alone. A comparison of the sequence selectivity of bleomycin in the presence of Cu and Fe using32P-end-labeled DNA duplexes as substrates revealed significant differences in sites of DNA cleavage and in the extent of cleavage at sites shared in common. For deglycobleomycin and decarbamoylbleomycin, whose metal ligation is believed to differ from that of bleomycin itself, it was found that the relative extents of DNA cleavage in the presence of Cu were not in the same order as those obtained in the presence of Fe. The results of these experiments are entirely consistent with the work of Sugiura who first demonstrate the generation of reactive oxygen species upon admixture of O2 and Cu(I)-bleomycin

  1. Synthesis and enzymatic cleavage of dual-ligand quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sewell, Sarah L. [Department of Biomedical Engineering, Vanderbilt University, Nashville, TN (United States); Giorgio, Todd D., E-mail: todd.d.giorgio@vanderbilt.edu [Department of Biomedical Engineering, Vanderbilt University, Nashville, TN (United States); Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN (United States)

    2009-05-05

    Site directed therapy promises to minimize treatment-limiting systemic effects associated with cytotoxic agents that have no specificity for pathologic tissues. One general strategy is to target cell surface receptors uniquely presented on particular tissues. Highly specific in vivo targeting of an emerging neoplasm through a single molecular recognition mechanism has not generally been successful. Nonspecific binding and specific binding to non-target cells compromise the therapeutic index of small molecule, ubiquitous cancer targeting ligands. In this work, we have designed and fabricated a nanoparticle (NP) construct that could potentially overcome the current limitations of targeted in vivo delivery. Quantum dots (QDs) were functionalized with a poly(ethylene glycol) (PEG) modified to enable specific cleavage by matrix metalloprotease-7 (MMP-7). The QDs were further functionalized with folic acid, a ligand for a cell surface receptor that is overexpressed in many tumors, but also expressed in some normal tissues. The nanomolecular construct is designed so that the PEG initially conceals the folate ligand and construct binding to cells is inhibited. MMP-7 activated peptide cleavage and subsequent unmasking of the folate ligand occurs only near tumor tissue, resulting in a proximity activated (PA) targeting system. QDs functionalized with both the MMP-7 cleavable substrate and folic acid were successfully synthesized and characterized. The proteolytic capability of the dual ligand QD construct was quantitatively assessed by fluorometric analysis and compared to a QD construct functionalized with only the PA ligand. The dual ligand PA nanoparticles studied here exhibit significant susceptibility to cleavage by MMP-7 at physiologically relevant conditions. The capacity to autonomously convert a biopassivated nanostructure to a tissue-specific targeted delivery agent in vivo represents a paradigm change for site-directed therapies.

  2. Synthesis and enzymatic cleavage of dual-ligand quantum dots

    International Nuclear Information System (INIS)

    Site directed therapy promises to minimize treatment-limiting systemic effects associated with cytotoxic agents that have no specificity for pathologic tissues. One general strategy is to target cell surface receptors uniquely presented on particular tissues. Highly specific in vivo targeting of an emerging neoplasm through a single molecular recognition mechanism has not generally been successful. Nonspecific binding and specific binding to non-target cells compromise the therapeutic index of small molecule, ubiquitous cancer targeting ligands. In this work, we have designed and fabricated a nanoparticle (NP) construct that could potentially overcome the current limitations of targeted in vivo delivery. Quantum dots (QDs) were functionalized with a poly(ethylene glycol) (PEG) modified to enable specific cleavage by matrix metalloprotease-7 (MMP-7). The QDs were further functionalized with folic acid, a ligand for a cell surface receptor that is overexpressed in many tumors, but also expressed in some normal tissues. The nanomolecular construct is designed so that the PEG initially conceals the folate ligand and construct binding to cells is inhibited. MMP-7 activated peptide cleavage and subsequent unmasking of the folate ligand occurs only near tumor tissue, resulting in a proximity activated (PA) targeting system. QDs functionalized with both the MMP-7 cleavable substrate and folic acid were successfully synthesized and characterized. The proteolytic capability of the dual ligand QD construct was quantitatively assessed by fluorometric analysis and compared to a QD construct functionalized with only the PA ligand. The dual ligand PA nanoparticles studied here exhibit significant susceptibility to cleavage by MMP-7 at physiologically relevant conditions. The capacity to autonomously convert a biopassivated nanostructure to a tissue-specific targeted delivery agent in vivo represents a paradigm change for site-directed therapies.

  3. Embryo apoptosis identification: Oocyte grade or cleavage stage?

    Science.gov (United States)

    Bakri, Noraina Mohd; Ibrahim, Siti Fatimah; Osman, Nurul Atikah; Hasan, Nurhaslina; Jaffar, Farah Hanan Fathihah; Rahman, Zulaiha Abdul; Osman, Khairul

    2016-01-01

    Apoptosis is a programed cell death that is vital for tissue homeostasis. However, embryo apoptosis had been known to be related to embryo fragmentation which should be avoided in in vitro fertilization (IVF). The purpose of this study was to evaluate the relationship of embryo apoptosis with the grade of immature oocytes and cleavage stage of in vitro produced (IVP) cattle embryos. This study consisted of 345 oocytes collected through ovary slicing. Immature oocytes were graded as A, B and C. This grading was based on cumulus cell thickness and compactness. All oocytes then underwent an in vitro maturation (IVM) procedure. An IVF was done 24 h after IVM culture. Prior to staining, stage of cleaved embryos was determined and classified as either 2, 4, 8 or >8-cell embryo stage. Apoptosis status of cleaved IVP embryos was determined by using annexin V-FITC staining technique at 48 and 72 h post insemination (hpi). Apoptosis status for each embryo was classified as either early or late. The result showed that there was no significant difference (p > 0.05) of apoptosis status among grade A, B and C embryos. All grades of oocytes showed embryo apoptosis where 1.5% late apoptosis for grade A, 4.5% and 10.4% of early and late apoptosis for grade B and grade C. Early apoptosis was not seen in grade A embryo. We also noted no significant difference (p > 0.05) of apoptosis status between 2, 4, 8 and >8-cell embryo stage. Early apoptosis was also not seen in >8-cell stage. Even though there were no differences in apoptosis expression between the three classes, the cleavage rate of grade A oocytes was significantly higher (p quality and the cleavage stage of the embryo produced. PMID:26858565

  4. Programmable RNA recognition and cleavage by CRISPR/Cas9

    OpenAIRE

    O’Connell, Mitchell R.; Oakes, Benjamin L.; Sternberg, Samuel H.; East-Seletsky, Alexandra; Kaplan, Matias; Doudna, Jennifer A.

    2014-01-01

    The CRISPR-associated protein Cas9 is an RNA-guided DNA endonuclease that uses RNA:DNA complementarity to identify target sites for sequence-specific doublestranded DNA (dsDNA) cleavage 1-5 . In its native context, Cas9 acts on DNA substrates exclusively because both binding and catalysis require recognition of a short DNA sequence, the protospacer adjacent motif (PAM), next to and on the strand opposite the 20-nucleotide target site in dsDNA 4-7 . Cas9 has proven to be a versatile tool for g...

  5. Features of Controlled Laser Thermal Cleavage of Crystalline Silicon

    International Nuclear Information System (INIS)

    Controlled laser thermal cleavage of crystalline silicon has been numerically simulated. A 3D analysis of the thermoelastic fields formed in a single-crystal silicon wafer as a result of successive laser heating and exposure to a coolant was performed for three different versions of anisotropy. The simulation was performed for laser irradiation with different wavelengths: 1.06 and 0.808 μm. The calculation results have been experimentally verified using a YAG laser. The results can be used in the electronics industry to optimize the precise separation of silicon wafers into crystals.

  6. Hydraulic Fracture Containment in Sand

    NARCIS (Netherlands)

    Dong, Y.

    2010-01-01

    The mechanism of hydraulic fracturing in soft, high permeability material is considered fundamentally different from that in hard, low permeability rock, where a tensile fracture is created and conventional linear elastic fracture mechanics (LEFM) applies. The fracturing and associated modeling work

  7. Fracture characteristics in Japanese rock

    International Nuclear Information System (INIS)

    It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the characteristics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified. (author)

  8. Analysis of the competition between brittle and ductile fracture: application for the mechanical behaviour of C-Mn and theirs welds

    International Nuclear Information System (INIS)

    This study deals with the fracture behaviour of welded thin structures in the ductile to brittle transition range. It aims to propose a criterion to define the conditions for which the risk of fracture by cleavage does not exist on a cracked structure. The literature review shows that the difficulties of prediction of the fracture behaviour of a structure are related to the dependence of the fracture probability to the mechanical fields at the crack tip. The ductile to brittle transition range thus depends on the studied geometry of the structure. A threshold stress, below which cleavage cannot take place, is defined using fracture tests on notched specimens broken at very low temperature. The finite element numerical simulation of fracture tests on CT specimens in the transition range shows a linear relationship between the fracture probability and the volume exceeding the threshold stress, thus showing the relevance of the proposed criterion. Moreover, several relations are established allowing to simplify the identification of the criterion parameters. The criterion is applied to a nuclear structural C-Mn steel, by focusing more particularly on the higher boundary of the transition range. A fracture test on a full-scale pipe is designed, developed, carried out and analysed using its numerical simulation. The results show firstly that, on the structure, the transition range is shifted in temperature, compared to laboratory specimens, due to the low plasticity constraint achieved in thin structures, and secondly that the threshold stress criterion allows to estimate simply this shift. (author)

  9. Fracture toughness evaluation of a low toughness weldment of reactor pressure vessel steel by ball indentation tests in the transition region

    International Nuclear Information System (INIS)

    Fracture toughness of the weldment of a pressure vessel steel was evaluated by ABI (automated ball indentation) tests in the transition temperature region. The evaluation procedure was based on the semi-empirical IEF (indentation energy to fracture) theory that has been recently developed using two basic assumptions. One is that the triaxial stress state beneath the ball indenter is similar to that of a crack tip ahead. Second, the fracture stress of a material is almost temperature-independent in case the stress-controlled cleavage fracture occurs. The fracture toughness characteristics determined by ABI tests were comparable to those obtained by standard 3-point bending tests. The multi-passed weldment was divided into two parts by their macroscopical appearances; as-solidified region and recrystallized one. However, both regions did not show a significant difference fracture toughness as well as hardness and flow properties in the tested material. (author)

  10. Stress fractures in athletes

    International Nuclear Information System (INIS)

    The early exclusion of the presence of a stress fracture may be decisive for the success of an athlete. Scintigraphy with a bone-seeking radiopharmaceutical is suitable for the early detection of stress lesions. Of 30 athletes, fractures were demonstrated in 17 whereas in 6 they were excluded. We found most fractures in the tarsal bones such as os naviculare pedis, ossa cuneiformia and talus. The type of sport engaged in appears to be an important factor in determining the location of the fracture. Scintiphotos were taken in several views using region of interest techniques and two phase-scintigraphy. This method is considered to be useful for localization and follow-up of skeletal stress lesions as well as for differential diagnosis. (orig.)

  11. Hip fracture - discharge

    Science.gov (United States)

    ... 2012:chap 55. Read More Broken bone Hip fracture surgery Hip pain Leg MRI scan Osteoporosis - overview Patient Instructions Getting your home ready - knee or hip surgery Osteomyelitis - discharge Update Date 11/ ...

  12. Ankle fracture - aftercare

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000548.htm Ankle fracture - aftercare To use the sharing features on this ... Sit with your foot elevated higher than your knee at least 4 times a day Apply an ...

  13. Hip fracture surgeries

    Science.gov (United States)

    ... nih.gov/pubmed/20837683 . Weinlein JC. Fractures and dislocations of the hip. In: Canale ST, Beaty JH, eds. Campbell's Operative ... Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, ...

  14. Fracture Mechanics of Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, Jens Peder

    Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high-strength......Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high......-strength concrete. Chapter 2 A description of the factors which influence the strength and cracking of concrete and high strength concrete is made. Then basic linear fracture mechanics is outlined followed by a description and evaluation of the models used to describe concrete fracture in tension. The chapter ends...

  15. Paediatric talus fracture.

    LENUS (Irish Health Repository)

    Byrne, Ann-Maria

    2012-01-01

    Paediatric talus fractures are rare injuries resulting from axial loading of the talus against the anterior tibia with the foot in dorsiflexion. Skeletally immature bone is less brittle, with higher elastic resistance than adult bone, thus the paediatric talus can sustain higher forces before fractures occur. However, displaced paediatric talus fractures and those associated with high-energy trauma have been associated with complications including avascular necrosis, arthrosis, delayed union, neurapraxia and the need for revision surgery. The authors present the rare case of a talar neck fracture in a skeletally immature young girl, initially missed on radiological review. However, clinical suspicion on the part of the emergency physician, repeat examination and further radiographic imaging revealed this rare paediatric injury.

  16. Metatarsal stress fractures - aftercare

    Science.gov (United States)

    ... blood pressure, kidney disease, or have had stomach ulcers or bleeding, talk with your doctor before using ... pain. When you restart an activity after a stress fracture, build up slowly. If your foot begins ...

  17. Classical fracture mechanics methods

    International Nuclear Information System (INIS)

    Comprehensive Structural Integrity is a reference work which covers all activities involved in the assurance of structural integrity. It provides engineers and scientists with an unparalleled depth of knowledge in the disciplines involved. The new online Volume 11 is dedicated to the mechanical characteristics of materials. This paper contains the chapter 11.02 of this volume and is structured as follows: Test techniques; Analysis; Fracture behavior; Fracture toughness tests for nonmetals

  18. Osteoporosis and Skeletal Fractures

    OpenAIRE

    Gardner, Michael J.; Demetrakopoulos, Demetris; Shindle, Michael K.; Griffith, Matthew H.; Lane, Joseph M.

    2006-01-01

    Osteoporosis affects millions of individuals worldwide, rendering them susceptible to fragility fractures of the spine, hip, and wrist and leading to significant morbidity, mortality, and economic cost. Given the substantial impact of osteoporosis on both patients and the medical community, it is imperative that physicians improve awareness and knowledge of osteoporosis in the setting of low-energy fractures. In this review, we provide information on effective means of preventing fragility fr...

  19. Relative permeability through fractures

    Energy Technology Data Exchange (ETDEWEB)

    Diomampo, Gracel, P.

    2001-08-01

    The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.

  20. Fractures on the calcaneus

    OpenAIRE

    Tanke, Gerhardus Marinus Henricus

    1982-01-01

    ln 823 patients with a displaced calcaneus fracturea study was carried out to assess the difference in the duration until recovery between those patients who were treated by operation and those who were treated conservatively. This was preceded by a study of the literature in which the accent was placed on the various types of calcaneus fractures regarding fracture mechanism, epidemiology, diagnostics and symptomatology as well as the different methods of treatment (chaptersl I to IV). ... Zi...

  1. Microscopic investigation of cleavage initiation in modified A508B pressure vessel steel

    International Nuclear Information System (INIS)

    A microscopic study on ductile-brittle crack growth in a modified version of the A508B pressure vessel steel has been performed. Small SEN(B)-specimens tested at different temperatures in and above the transition region have been thoroughly examined with a scanning electron microscope. Focus was directed towards: amount of ductile crack growth prior to cleavage, distance from the crack front to cleavage initiation sites, and type of defect that caused the cleavage initiation. The results show, among other things, that cleavage facets are present in specimens tested at all temperatures, even on the upper shelf where no global failure by cleavage was observed. These preliminary results give an indication that the ability of the matrix material to arrest and sustain small cleavage cracks can be crucial in explaining why ferritic steels show a transition behaviour. (orig.)

  2. FRACTURING FLUID CHARACTERIZATION FACILITY

    Energy Technology Data Exchange (ETDEWEB)

    Subhash Shah

    2000-08-01

    Hydraulic fracturing technology has been successfully applied for well stimulation of low and high permeability reservoirs for numerous years. Treatment optimization and improved economics have always been the key to the success and it is more so when the reservoirs under consideration are marginal. Fluids are widely used for the stimulation of wells. The Fracturing Fluid Characterization Facility (FFCF) has been established to provide the accurate prediction of the behavior of complex fracturing fluids under downhole conditions. The primary focus of the facility is to provide valuable insight into the various mechanisms that govern the flow of fracturing fluids and slurries through hydraulically created fractures. During the time between September 30, 1992, and March 31, 2000, the research efforts were devoted to the areas of fluid rheology, proppant transport, proppant flowback, dynamic fluid loss, perforation pressure losses, and frictional pressure losses. In this regard, a unique above-the-ground fracture simulator was designed and constructed at the FFCF, labeled ''The High Pressure Simulator'' (HPS). The FFCF is now available to industry for characterizing and understanding the behavior of complex fluid systems. To better reflect and encompass the broad spectrum of the petroleum industry, the FFCF now operates under a new name of ''The Well Construction Technology Center'' (WCTC). This report documents the summary of the activities performed during 1992-2000 at the FFCF.

  3. Drosha regulates gene expression independently of RNA cleavage function

    DEFF Research Database (Denmark)

    Gromak, Natalia; Dienstbier, Martin; Macias, Sara;

    2013-01-01

    Drosha is the main RNase III-like enzyme involved in the process of microRNA (miRNA) biogenesis in the nucleus. Using whole-genome ChIP-on-chip analysis, we demonstrate that, in addition to miRNA sequences, Drosha specifically binds promoter-proximal regions of many human genes in a transcription......-terminal protein-interaction domain, which associates with the RNA-binding protein CBP80 and RNA Polymerase II. Consequently, we uncover a previously unsuspected RNA cleavage-independent function of Drosha in the regulation of human gene expression.......Drosha is the main RNase III-like enzyme involved in the process of microRNA (miRNA) biogenesis in the nucleus. Using whole-genome ChIP-on-chip analysis, we demonstrate that, in addition to miRNA sequences, Drosha specifically binds promoter-proximal regions of many human genes in a transcription......-dependent manner. This binding is not associated with miRNA production or RNA cleavage. Drosha knockdown in HeLa cells downregulated nascent gene transcription, resulting in a reduction of polyadenylated mRNA produced from these gene regions. Furthermore, we show that this function of Drosha is dependent on its N...

  4. Effect of temperature on tensile fracture mechanisms of a Ni-base superalloy

    Directory of Open Access Journals (Sweden)

    S.M. Zebarjad

    2007-01-01

    Full Text Available Purpose: The Ni-base superalloy GTD-111 is used in manufacturing of the first stage blades of powerful gas turbines (over 125MW. The alloy posses appropriate microstructure and high temperature properties through precipitation hardening heat treatment. Among the properties, tensile properties of the alloy have strong influence on stability and life of the blades.Design/methodology/approach: Tensile tests over a wide range of temperatures from 25 to 950°C with a constant strain rate of 10-4s-1 were performed to study the tensile fracture mechanisms of the cast and heat treated superalloy. Scanning electron microscopy was used to provide structural and fractography evidence of the superalloy GTD-111at different temperatures.Findings: The fractography results of the tensile tested specimens were in good agreement with the variation in alloy ductility. Many fractography features such as: transgranular and intergranular fracture with fine dimples, cleavage facets and a combination of them were observed in the specimens tested at different temperatures.Research limitations/implications: Because fatigue is an important fracture mechanism at the service condition of the alloy it is suggested for future research to work on the simultaneous effects of tension and fatigue on the fracture mechanisms although, tensile properties alone are important for the alloy.Originality/value: It was found that different fracture mechanisms operated in different temperature ranges for example, while transgranular dimple fracture was dominant at 650°C, the dominant fracture mechanism at room temperature was intergranular.

  5. Potential impact of enhanced fracture-toughness data on pressurized-thermal-shock analysis

    International Nuclear Information System (INIS)

    The Heavy Section Steel Technology (HSST) Program is involved with the generation of 'enhanced' fracture-initiation toughness and fracture-arrest toughness data of prototypic nuclear reactor vessel steels. These two sets of data are enhanced because they have distinguishing characteristics that could potentially impact PWR pressure vessel integrity assessments for the pressurized-thermal shock (PTS) loading condition which is a major plant-life extension issue to be confronted in the 1990's. Over the past several years, the HSST Program at Oak Ridge National Laboratory (ORNL) has performed a series of large-scale fracture- mechanics experiments. These experiments have produced crack-arrest (KIa) data with the distinguishing characteristic that the values are considerably above 220 MPa · √m, the implicit limit of the ASME Code and the limit used in the Integrated Pressurized Thermal Shock (IPTS) studies. Currently, the HSST Program is planning experiments to verify and quantify, for A533B steel, the distinguishing characteristic of elevated initiation-fracture toughness for shallow flaws which has been observed for other steels. Deterministic and probabilistic fracture-mechanics analyses were performed to examine the influence of the enhanced initiation and arrest fracture- toughness data on the cleavage fracture response of a nuclear reactor pressure vessel subjected to PTS loading

  6. Mechanical strength and analysis of fracture of titanium joining submitted to laser and tig welding

    Directory of Open Access Journals (Sweden)

    Ana Cláudia Gabrielli Piveta

    2012-12-01

    Full Text Available This study compared the tensile strength and fracture mechanism of tungsten inert gas (TIG welds in cylindrical rods of commercially pure titanium (cp Ti with those of laser welds and intact samples. Thirty dumbbell-shaped samples were developed by using brass rods as patterns. The samples were invested in casings, subjected to thermal cycles, and positioned in a plasma arc welding machine under argon atmosphere and vacuum, and titanium was injected under vacuum/pressure. The samples were X-rayed to detect possible welding flaws and randomly assigned to three groups to test the tensile strength and the fracture mechanism: intact, laser welding, and TIG welding. The tensile test results were investigated using ANOVA, which indicated that the samples were statistically similar. The fracture analysis showed that the cpTi samples subjected to laser welding exhibited brittle fracture and those subjected to TIG welding exhibited mixed brittle/ductile fracture with a predominance of ductile fracture with the presence of microcavities and cleavage areas. Intact samples presented the characteristic straightening in the fracture areas, indicating the ductility of the material.

  7. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture-toughness

    International Nuclear Information System (INIS)

    Uniaxial tests of single-edged notched bend (SENB) specimens with both deep- and shallow-flaws have shown elevated fracture-toughness for the shallow flaws. The elevation in fracture-toughness for shallow flaws has been shown to be the result of reduced constraint at the crack-tip. Biaxial loading has the potential to increase constraint at the crack-tip and thereby reduce some of the shallow-flaw, fracture-toughness elevation. Biaxial fracture-toughness tests have shown that the shallow-flaw, fracture-toughness elevation is reduced but not eliminated by biaxial loading. Dual-parameter, fracture-toughness correlations have been proposed to reflect the effect of crack-tip constraint on fracture-toughness. Test results from the uniaxial and biaxial tests were analyzed using the dual-parameter technology. Discrepancies between analysis results and cleavage initiation site data from fractographic examinations indicate that the analysis models are in need of further refinement. Addition of a precleavage, ductile-tearing element to the analysis model has the potential to resolve the noted discrepancies

  8. Intracellular ribozyme-catalyzed trans-cleavage of RNA monitored by fluorescence resonance energy transfer.

    OpenAIRE

    Vitiello, D; Pecchia, D B; Burke, J M

    2000-01-01

    Small catalytic RNAs like the hairpin ribozyme are proving to be useful intracellular tools; however, most attempts to demonstrate trans-cleavage of RNA by ribozymes in cells have been frustrated by rapid cellular degradation of the cleavage products. Here, we describe a fluorescence resonance energy transfer (FRET) assay that directly monitors cleavage of target RNA in tissue-culture cells. An oligoribonucleotide substrate was modified to inhibit cellular ribonuclease degradation without int...

  9. A pathway sensor for genome-wide screens of intracellular proteolytic cleavage

    OpenAIRE

    Ketteler, Robin; Sun, Zairen; Kovacs, Karl F; He, Wei-Wu; Seed, Brian

    2008-01-01

    Protein cleavage is a central event in many regulated biological processes. We describe a system for detecting intracellular proteolysis based on non-conventional secretion of Gaussia luciferase (GLUC). GLUC exits the cell without benefit of a secretory leader peptide, but can be anchored in the cell by fusion to \\(\\beta\\)-actin. By including protease cleavage sites between GLUC and \\(\\beta\\)-actin, proteolytic cleavage can be detected. Using this assay, we have identified regulators of autop...

  10. A real-time assay for monitoring nucleic acid cleavage by quadruplex formation

    OpenAIRE

    Kankia, Besik I.

    2006-01-01

    Direct and straightforward methods to follow nucleic acid cleavage are needed. A spectrophotometric quadruplex formation assay (QFA) was developed, which allows real-time monitoring of site-specific cleavage of nucleic acids. QFA was applied to study both protein and nucleic acid restriction enzymes, and was demonstrated to accurately determine Michaelis–Menten parameters for the cleavage reaction catalyzed by EcoRI. QFA can be used to study the mechanisms of protein–nucleic acid recognition....

  11. Characterization of the Microstructure, Fracture, and Mechanical Properties of Aluminum Alloys 7085-O and 7175-T7452 Hollow Cylinder Extrusions

    Science.gov (United States)

    Benoit, Samuel G.; Chalivendra, Vijaya B.; Rice, Matthew A.; Doleski, Robert F.

    2016-06-01

    Microstructural, tensile, and fracture characterizations of cylindrically forged forms of aluminum alloys AA7085-O and AA7175-T7452 were performed. Mechanical and fracture properties were investigated along radial, circumferential, and longitudinal directions to determine directional dependency. American Society for Testing and Materials (ASTM) test methods (ASTM E8-04 and ASTM E1820) were employed for both the tensile and fracture characterizations, respectively. The tensile and fracture properties were related to microstructure in each direction. The strength, elongation at break, and ultimate tensile strength of AA7085-O were higher than those of AA7175-T7452. AA7175-T7452 alloy failed in a brittle manner during fracture studies. AA7085-O outperformed AA7175-T7452 on fracture energy in all of the orientations studied. Smaller grain sizes on the planes normal to circumferential and longitudinal directions showed improvement in both elongation at break and fracture energy values compared to those of radial direction. Scanning electron microscopy images demonstrated cleavage fracture in AA7175-T7452 and transgranular fracture in AA7085-O.

  12. CT of pelvic fractures

    Energy Technology Data Exchange (ETDEWEB)

    Falchi, Marco E-mail: marcofalchi@yahoo.it; Rollandi, Gian Andrea

    2004-04-01

    Although magnetic resonance imaging has become the dominant modality for cross-sectional musculo-skeletal imaging, the widespread availability, speed, and versatility of computed tomography (CT) continue to make it a mainstay of emergency room (ER) diagnostic imaging. Pelvic ring and acetabular fractures occur as the result of significant trauma secondary to either a motor vehicle accident or a high-velocity fall. These injuries are correlated with significant morbidity and mortality, both from the complications of pelvic ring fractures and from commonly associated injuries. The most commonly used classification of pelvic and acetabular fractures has been based on conventional radiographs that are, in the majority of cases, sufficient to determine the type of injury. However, because of the complexity of pelvic and acetabular fractures, precise pathological anatomy is not easily demonstrated by routine radiographs and in many cases details of fractures are not visible. Moreover, the insufficient co-operation of the patient or the difficulty of maintaining special positions can be overcome by using computed tomography. Spiral computed tomography provides information regarding the extent of the fractures and is complementary to radiography for ascertaining the spatial arrangement of fracture fragments. Spiral computed tomography is an effective tool for understanding complex fracture patterns, particularly when combined with multi-planar reconstruction two-dimensional (MPR 2D) reformatted images or three-dimensional images (3D) images. Including these techniques of reconstruction in routine pelvic imaging protocols can change management in a significant number of cases. Subtle fractures, particularly those oriented in the axial plane, are better seen on MPR images or 3D volume-rendered images. Complex injuries can be better demonstrated with 3D volume-rendered images, and complicated spatial information about the relative positions of fracture fragments can be easily

  13. CT of pelvic fractures

    International Nuclear Information System (INIS)

    Although magnetic resonance imaging has become the dominant modality for cross-sectional musculo-skeletal imaging, the widespread availability, speed, and versatility of computed tomography (CT) continue to make it a mainstay of emergency room (ER) diagnostic imaging. Pelvic ring and acetabular fractures occur as the result of significant trauma secondary to either a motor vehicle accident or a high-velocity fall. These injuries are correlated with significant morbidity and mortality, both from the complications of pelvic ring fractures and from commonly associated injuries. The most commonly used classification of pelvic and acetabular fractures has been based on conventional radiographs that are, in the majority of cases, sufficient to determine the type of injury. However, because of the complexity of pelvic and acetabular fractures, precise pathological anatomy is not easily demonstrated by routine radiographs and in many cases details of fractures are not visible. Moreover, the insufficient co-operation of the patient or the difficulty of maintaining special positions can be overcome by using computed tomography. Spiral computed tomography provides information regarding the extent of the fractures and is complementary to radiography for ascertaining the spatial arrangement of fracture fragments. Spiral computed tomography is an effective tool for understanding complex fracture patterns, particularly when combined with multi-planar reconstruction two-dimensional (MPR 2D) reformatted images or three-dimensional images (3D) images. Including these techniques of reconstruction in routine pelvic imaging protocols can change management in a significant number of cases. Subtle fractures, particularly those oriented in the axial plane, are better seen on MPR images or 3D volume-rendered images. Complex injuries can be better demonstrated with 3D volume-rendered images, and complicated spatial information about the relative positions of fracture fragments can be easily

  14. RNase II is important for A-site mRNA cleavage during ribosome pausing

    OpenAIRE

    Garza-Sánchez, Fernando; Shoji, Shinichiro; Fredrick, Kurt; Hayes, Christopher S.

    2009-01-01

    In Escherichia coli, translational arrest can elicit cleavage of codons within the ribosomal A site. This A-site mRNA cleavage is independent of RelE, and has been proposed to be an endonucleolytic activity of the ribosome. Here, we show that the 3′→5′ exonuclease RNase II plays an important role in RelE-independent A-site cleavage. Instead of A-site cleavage, translational pausing in ΔRNase II cells produces transcripts that are truncated +12 and +28 nucleotides downstream of the A-site codo...

  15. Hairpin DNA Sequences Bound Strongly by Bleomycin Exhibit Enhanced Double-Strand Cleavage

    OpenAIRE

    Roy, Basab; Hecht, Sidney M.

    2014-01-01

    Clinically used bleomycin A5 has been employed in a study of double-strand cleavage of a library of 10 hairpin DNAs originally selected on the basis of their strong binding to bleomycin. Each of the DNAs underwent double-strand cleavage at more than one site, and all of the cleavage sites were within, or in close proximity to, an eight-base-pair region of the duplex that had been randomized to create the original library. A total of 31 double-strand cleavage sites were identified on the 10 DN...

  16. The First Example of Cation Radical Induced Ether Cleavage of Benzyl Phenyl Ether

    International Nuclear Information System (INIS)

    A thermally stable benzyl phenyl ether has been shown to cleavage under mild conditions. The new reaction described herein further expands the chemistry of the ether cleavage by cation radicals. Over the last several years, our lab has discovered cation radical-induced oxidative C-O bond cleavages such as carbonates (eq 1), carbamates (eq 2), peroxides (eq 3), and alcohols (eq 4), where R is either tert-butyl or benzyl. It was recognized from those reactions that carbocationic chemistry with C-O bond cleavages was predominant, with a 2:1 stoichiometry of Th+·:oxidized molecules

  17. Cleavage of RseA by RseP requires a carboxyl-terminal hydrophobic amino acid following DegS cleavage

    OpenAIRE

    Li, Xiaochun; Wang, Boyuan; Feng, Lihui; Kang, Hui; Qi, Yang; Wang, Jiawei; Shi, Yigong

    2009-01-01

    Regulated intramembrane proteolysis (RIP) by the Site-2 protease (S2P) results in the release of a transmembrane signaling protein. Curiously, however, S2P cleavage must be preceded by the action of the Site-1 protease (S1P). To decipher the underlying mechanism, we reconstituted sequential, in vitro cleavages of the Escherichia coli transmembrane protein RseA by DegS (S1P) and RseP (S2P). After DegS cleavage, the newly exposed carboxyl-terminal residue Val-148 of RseA plays an essential role...

  18. Specific pre-cleavage and post-cleavage complexes involved in the formation of SV40 late mRNA 3' termini in vitro.

    OpenAIRE

    Zarkower, D; Wickens, M

    1987-01-01

    Complexes form between processing factors present in a crude nuclear extract from HeLa cells and a simian virus 40 (SV40) late pre-mRNA which spans the polyadenylation [poly(A)] site. A specific 'pre-cleavage complex' forms on the pre-mRNA before cleavage. Formation of this complex requires the highly conserved sequence AAUAAA: it is prevented by mutations in AAUAAA, and by annealing DNA oligonucleotides to that sequence. After cleavage, the 5' half-molecule is found in a distinct 'post-cleav...

  19. Occult fracture of the calcaneus - another Toddler's fracture

    International Nuclear Information System (INIS)

    Fractures of the calcaneus have been considered rare among children. We feel this may be erroneous since in the last 12 months we have seen 10 such fractures among children, 19 and 41 months of age, who presented with acute limping. The fractures were detected with bone imaging which was performed when initial radiographs were noncontributory. Subsequent radiographs of the calcaneus were positive for fracture in 4 to 10 while follow up radiographs confirmed healing fractures in the two children so evaluated. The sensitivity of bone imaging for the detection of occult fractures in toddlers is emphasized. (orig.)

  20. Aperture distribution of rock fractures

    International Nuclear Information System (INIS)

    This thesis concerns the properties of the fracture void geometry of single rock fractures. It is suggested that the parameter aperture be used to describe the fracture void geometry and a definition of the aperture is proposed. The relation between void geometry and other fracture properties such as roughness, stiffness, conductivity and channelling are discussed. Different experimental techniques for aperture measurement have been developed in this work. The methods are applicable to fractures of different nature and size. A compilation of measurement results indicates that the spatial correlation (range) of fracture apertures increases with increasing mean aperture and that the range is correlated with the coefficient of variation. The existing data from aperture measurements and fracture flow experiments are still very scarce, in particular for fractures with large apertures. For future research, additional aperture measurements from fractures of different types is recommended. A further development of aperture measurement techniques suitable for field investigation is also suggested. 31 refs, 18 figs

  1. An experimental study on the deformation and fracture modes of steel projectiles during impact

    International Nuclear Information System (INIS)

    Highlights: • The fracture process is ductile for the unhardened projectiles. • A combined ductile–brittle fracture process is obtained for the HRC 40 projectiles. • The fragmentation of HRC 52 projectiles has cleavage as the main mechanism. • The fracture modes were confirmed in a metallurgical study. • The hardened materials have a stochastic variation of the mechanical properties. - Abstract: Previous investigations of the penetration and perforation of high-strength steel plates struck by hardened steel projectiles have shown that under certain test conditions the projectile may fracture or even fragment upon impact. Simulations without an accurate failure description for the projectile material will then predict perforation of the target instead of fragmentation of the projectile, and thus underestimate the ballistic limit velocity of the target plate. This paper presents an experimental investigation of the various deformation and fracture modes that may occur in steel projectiles during impact. This is studied by conducting Taylor bar impact tests using 20 mm diameter, 80 mm long, tool steel projectiles with three different hardness values (HRC 19, 40 and 52). A gas gun was used to fire the projectiles into a rigid wall at impact velocities ranging from 100 to 350 m/s, and the deformation and fracture processes were captured by a high-speed video camera. From the tests, several different deformation and fracture modes were registered for each hardness value. To investigate the influence of material on the deformation and fracture modes, several series of tensile tests on smooth axisymmetric specimens were carried out to characterise the mechanical properties of the three materials. To gain a deeper understanding of the various processes causing fracture and fragmentation during impact, a metallurgical investigation was conducted. The fracture surfaces of the failed projectiles of different hardness were investigated, and the microstructure was

  2. Embryo apoptosis identification: Oocyte grade or cleavage stage?

    Science.gov (United States)

    Bakri, Noraina Mohd; Ibrahim, Siti Fatimah; Osman, Nurul Atikah; Hasan, Nurhaslina; Jaffar, Farah Hanan Fathihah; Rahman, Zulaiha Abdul; Osman, Khairul

    2015-01-01

    Apoptosis is a programed cell death that is vital for tissue homeostasis. However, embryo apoptosis had been known to be related to embryo fragmentation which should be avoided in in vitro fertilization (IVF). The purpose of this study was to evaluate the relationship of embryo apoptosis with the grade of immature oocytes and cleavage stage of in vitro produced (IVP) cattle embryos. This study consisted of 345 oocytes collected through ovary slicing. Immature oocytes were graded as A, B and C. This grading was based on cumulus cell thickness and compactness. All oocytes then underwent an in vitro maturation (IVM) procedure. An IVF was done 24 h after IVM culture. Prior to staining, stage of cleaved embryos was determined and classified as either 2, 4, 8 or >8-cell embryo stage. Apoptosis status of cleaved IVP embryos was determined by using annexin V-FITC staining technique at 48 and 72 h post insemination (hpi). Apoptosis status for each embryo was classified as either early or late. The result showed that there was no significant difference (p > 0.05) of apoptosis status among grade A, B and C embryos. All grades of oocytes showed embryo apoptosis where 1.5% late apoptosis for grade A, 4.5% and 10.4% of early and late apoptosis for grade B and grade C. Early apoptosis was not seen in grade A embryo. We also noted no significant difference (p > 0.05) of apoptosis status between 2, 4, 8 and >8-cell embryo stage. Early apoptosis was also not seen in >8-cell stage. Even though there were no differences in apoptosis expression between the three classes, the cleavage rate of grade A oocytes was significantly higher (p < 0.01) than grade B and grade C. In conclusion, the apoptosis expression in the embryo can occur regardless of the oocyte quality and the cleavage stage of the embryo produced. PMID:26858565

  3. Radiological classification of mandibular fractures

    International Nuclear Information System (INIS)

    Mandibular fractures present the biggest part (up to 97%) of the facial bone fractures. Method of choice for diagnosing of mandibular fractures is conventional radiography. The aim of the issue is to present an unified radiological classification of mandibular fractures for the clinical practice. This classification includes only those clinical symptoms of mandibular fracture which could be radiologically objectified: exact anatomical localization (F1-F6), teeth in fracture line (Ta,Tb), grade of dislocation (D I, D II), occlusal disturbances (O(+), O(-)). Radiological symptoms expressed by letter and number symbols are systematized in a formula - FTDO of mandibular fractures similar to TNM formula for tumours. FTDO formula expresses radiological diagnose of each mandibular fracture but it doesn't include neither the site (left or right) of the fracture, nor the kind and number of fractures. In order to express topography and number of fractures the radiological formula is transformed into a decimal fraction. The symbols (FTD) of right mandible fracture are written in the numerator and those of the left site - in the denominator. For double and multiple fractures between the symbols for each fracture we put '+'. Symbols for occlusal disturbances are put down opposite, the fractional line. So topographo-anatomical formula (FTD/FTD)xO is formed. In this way the whole radiological information for unilateral, bilateral, single or multiple fractures of the mandible is expressed. The information in the radiological topography anatomic formula, resp. from the unified topography-anatomic classification ensures a quick and exact X-ray diagnose of mandibular fracture. In this way contributes to get better, make easier and faster X-ray diagnostic process concerning mandibular fractures. And all these is a precondition for prevention of retardation of the diagnosis mandibular fracture. (author)

  4. Carpal fractures in athletes.

    Science.gov (United States)

    Geissler, W B

    2001-01-01

    A review of the literature shows that 3% to 9% of all athletic injuries occur to the hand or wrist. Also, hand and wrist injuries are more common in pubescent and adolescent athletes than adults. Although knee and shoulder injuries are more common athletic injuries, an injury to the hand or wrist significantly can impair the athlete's ability to throw or catch a ball, or swing a bat or racquet. A college football player trains year round for just 11 or 12 hours of playing time. An athletic injury that occurs during the season can have profound consequences for the athlete's career and emotions. When defining a management plan for a particular wrist athletic injury, the time to heal the injury and the time to rehabilitate fully must be considered. The athlete must be informed fully of the length of recovery. The continued advancement of fixation methods and techniques are diminishing fracture morbidity considerably. Small-cannulated compression screws that provide rigid fixation can be inserted with decreased surgical dissection, thus preserving critical vascular supply and promoting accelerated healing and earlier rehabilitation. The arthroscope as a valuable adjunct in the management of wrist fractures was virtually unheard of years ago, but is now common. The ability to arthroscopically guide a cannulated compression screw to stabilize a scaphoid fracture without a formal open volar approach can reduce surgical morbidity significantly and allow the athlete to return to competition more quickly. Mechanisms of injury that cause osseous fractures of the wrist are fairly high energy. A high index of suspicion for associated soft tissue injuries should be kept in mind when fractures of the wrist are identified. The wrist is composed of eight carpal bones tightly interwoven with each other by intrinsic and extrinsic wrist ligaments. The management of carpal fractures depends on prompt diagnosis, stable and anatomic alignment of the involved carpal bone, protective

  5. Management of penile fractures

    International Nuclear Information System (INIS)

    Objective was to present our experience with surgical and conservative management of penile fracture. This prospective study was carried out in the Urology and Nephrology Center, at Al-Thawra General and Teaching Hospital, Sana'a, Yemen from June 2003 to September 2007 and included 30 patients presenting with penile fracture. Diagnosis was made clinically in all our patients. Six patients with simple fracture were treated conservatively while 24 patients with more severe injuries were operated upon. Patient's age ranged from 24-52 years (mean 31.3 years) 46.7% of patients were under the age of 30 years and 56.7% were unmarried. Hard manipulation of the erect penis for example during masturbation was the most frequent mechanism of fracture in 53.3% of patients. Solitary tear was found in 22 patients and bilateral corporal tears associated with urethral injury were found in 2 patients. Corporal tears were saturated with synthetic absorbable sutures and urethral injury was repaired primarily. All operated patients described full erection with straight penis except 3 of the 8 patients who were managed by direct longitudinal incision, in whom mild curvature during erection was observed. The conservatively treated patients described satisfactory penile straightness and erection. The optimal functional and cosmetic results are achieved following immediate surgical repair of penis fracture. Good results can also be obtained in some selected patients with conservative management. (author)

  6. Stress fractures in athletes

    International Nuclear Information System (INIS)

    Stress fractures may pose a diagnostic dilemma for radiologists since they are sometimes difficult to demonstrate on plain films and may simulate a tumour. They were first described in military personnel and professional athletes. Recently, there is an increasing incidence in the general population due to increasing sportive activities. Stress fractures occur most often in the lower extremities, especially in the tibia, the tarsal bone, the metatarsal bone, the femur and the fibula. In the upper extremities, they are commonly found in the humerus, the radius and the ulna. Some fractures of the lower extremities appear to be specific for particular sports, for example, fractures of the tibia affect mostly distance runners. Whereas stress fractures of the upper extremities are generally associated with upper limb-dominated sports. A correct diagnosis requires a careful clinical evaluation. The initial plain radiography may be normal. Further radiological evaluation could be performed by means of computerised tomography, magnetic resonance imaging and bone scanning. The latter two techniques are especially helpful for establishing a correct initial diagnosis. (orig.)

  7. Fractures mechanics. Pt. 30

    International Nuclear Information System (INIS)

    This book results from lectures which the author held front of students in engineering, and it is aimed at giving an introduction into the linear elasticity fracture mechanics. A dominant part of the contents deals with theoretical elasticity solutions of fracture problems, the foundation of the theories of friffith and Irwin concerning crack expansion and fractures, respectively. Besides, the propects of development in the direction of general flow fracture mechanics are investigated, a development which cannot be regarded as conclusive yet. The reference - it is not claimed that they are comprehensive - contain some basic manuals and monographies on fractures, the elasticity theory and the science of strength of materials as well as related fields, and include also important original literature made reference to in the text. In order to comprehend the book it is necessary that the reader has a knowledge of technical mechanics, in particular of elastotatics and strength of materials. To remind the reader, the appendix contains the most important basics of the elasticity theory and some methods of solving problems in this connection. The book ends with a short survey on the finite element method which is considered to be the most important approximation method of continuum mechanics. (orig./LN)

  8. Atomistic Simulations of Nanotube Fracture

    CERN Document Server

    Belytschko, T; Schatz, G; Ruoff, R S

    2002-01-01

    The fracture of carbon nanotubes is studied by atomistic simulations. The fracture behavior is found to be almost independent of the separation energy and to depend primarily on the inflection point in the interatomic potential. The rangle of fracture strians compares well with experimental results, but predicted range of fracture stresses is marketly higher than observed. Various plausible small-scale defects do not suffice to bring the failure stresses into agreement with available experimental results. As in the experiments, the fracture of carbon nanotubes is predicted to be brittle. The results show moderate dependence of fracture strength on chirality.

  9. Catalysts of DNA Strand Cleavage at Apurinic/Apyrimidinic Sites.

    Science.gov (United States)

    Minko, Irina G; Jacobs, Aaron C; de Leon, Arnie R; Gruppi, Francesca; Donley, Nathan; Harris, Thomas M; Rizzo, Carmelo J; McCullough, Amanda K; Lloyd, R Stephen

    2016-01-01

    Apurinic/apyrimidinic (AP) sites are constantly formed in cellular DNA due to instability of the glycosidic bond, particularly at purines and various oxidized, alkylated, or otherwise damaged nucleobases. AP sites are also generated by DNA glycosylases that initiate DNA base excision repair. These lesions represent a significant block to DNA replication and are extremely mutagenic. Some DNA glycosylases possess AP lyase activities that nick the DNA strand at the deoxyribose moiety via a β- or β,δ-elimination reaction. Various amines can incise AP sites via a similar mechanism, but this non-enzymatic cleavage typically requires high reagent concentrations. Herein, we describe a new class of small molecules that function at low micromolar concentrations as both β- and β,δ-elimination catalysts at AP sites. Structure-activity relationships have established several characteristics that appear to be necessary for the formation of an iminium ion intermediate that self-catalyzes the elimination at the deoxyribose ring. PMID:27363485

  10. Cleavage of an amide bond by a ribozyme

    Science.gov (United States)

    Dai, X.; De Mesmaeker, A.; Joyce, G. F.; Miller, S. L. (Principal Investigator)

    1995-01-01

    A variant form of a group I ribozyme, optimized by in vitro evolution for its ability to catalyze magnesium-dependent phosphoester transfer reactions involving DNA substrates, also catalyzes the cleavage of an unactivated alkyl amide when that linkage is presented in the context of an oligodeoxynucleotide analog. Substrates containing an amide bond that joins either two DNA oligos, or a DNA oligo and a short peptide, are cleaved in a magnesium-dependent fashion to generate the expected products. The first-order rate constant, kcat, is 0.1 x 10(-5) min-1 to 1 x 10(-5) min-1 for the DNA-flanked substrates, which corresponds to a rate acceleration of more than 10(3) as compared with the uncatalyzed reaction.

  11. Dinitrogen cleavage and hydrogenation by a trinuclear titanium polyhydride complex.

    Science.gov (United States)

    Shima, Takanori; Hu, Shaowei; Luo, Gen; Kang, Xiaohui; Luo, Yi; Hou, Zhaomin

    2013-06-28

    Both the Haber-Bosch and biological ammonia syntheses are thought to rely on the cooperation of multiple metals in breaking the strong N≡N triple bond and forming an N-H bond. This has spurred investigations of the reactivity of molecular multimetallic hydrides with dinitrogen. We report here the reaction of a trinuclear titanium polyhydride complex with dinitrogen, which induces dinitrogen cleavage and partial hydrogenation at ambient temperature and pressure. By (1)H and (15)N nuclear magnetic resonance, x-ray crystallographic, and computational studies of some key reaction steps and products, we have determined that the dinitrogen (N2) reduction proceeds sequentially through scission of a N2 molecule bonded to three Ti atoms in a μ-η(1):η(2):η(2)-end-on-side-on fashion to give a μ2-N/μ3-N dinitrido species, followed by intramolecular hydrogen migration from Ti to the μ2-N nitrido unit. PMID:23812710

  12. Fracture-Flow-Enhanced Solute Diffusion into Fractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yu-Shu; Ye, Ming; Sudicky, E.A.

    2007-12-15

    We propose a new conceptual model of fracture-flow-enhanced matrix diffusion, which correlates with fracture-flow velocity, i.e., matrix diffusion enhancement induced by rapid fluid flow within fractures. According to the boundary-layer or film theory, fracture flow enhanced matrix diffusion may dominate mass-transfer processes at fracture-matrix interfaces, because rapid flow along fractures results in large velocity and concentration gradients at and near fracture-matrix interfaces, enhancing matrix diffusion at matrix surfaces. In this paper, we present a new formulation of the conceptual model for enhanced fracture-matrix diffusion, and its implementation is discussed using existing analytical solutions and numerical models. In addition, we use the enhanced matrix diffusion concept to analyze laboratory experimental results from nonreactive and reactive tracer breakthrough tests, in an effort to validate the new conceptual model.

  13. Delay of HeLa cell cleavage into interphase using dihydrocytochalasin B: retention of a postmitotic spindle and telophase disc correlates with synchronous cleavage recovery

    OpenAIRE

    1995-01-01

    The molecular signals that determine the position and timing of the cleavage furrow during mammalian cell cytokinesis are presently unknown. We have studied in detail the effect of dihydrocytochalasin B (DCB), a drug that interferes with actin assembly, on specific late mitotic events in synchronous HeLa cells. When cleavage furrow formation is blocked at 10 microM DCB, cells return to interphase by the criteria of reformation of nuclei with lamin borders, degradation of the cyclin B componen...

  14. SARS coronavirus nsp1 protein induces template-dependent endonucleolytic cleavage of mRNAs: viral mRNAs are resistant to nsp1-induced RNA cleavage.

    Directory of Open Access Journals (Sweden)

    Cheng Huang

    2011-12-01

    Full Text Available SARS coronavirus (SCoV nonstructural protein (nsp 1, a potent inhibitor of host gene expression, possesses a unique mode of action: it binds to 40S ribosomes to inactivate their translation functions and induces host mRNA degradation. Our previous study demonstrated that nsp1 induces RNA modification near the 5'-end of a reporter mRNA having a short 5' untranslated region and RNA cleavage in the encephalomyocarditis virus internal ribosome entry site (IRES region of a dicistronic RNA template, but not in those IRES elements from hepatitis C or cricket paralysis viruses. By using primarily cell-free, in vitro translation systems, the present study revealed that the nsp1 induced endonucleolytic RNA cleavage mainly near the 5' untranslated region of capped mRNA templates. Experiments using dicistronic mRNAs carrying different IRESes showed that nsp1 induced endonucleolytic RNA cleavage within the ribosome loading region of type I and type II picornavirus IRES elements, but not that of classical swine fever virus IRES, which is characterized as a hepatitis C virus-like IRES. The nsp1-induced RNA cleavage of template mRNAs exhibited no apparent preference for a specific nucleotide sequence at the RNA cleavage sites. Remarkably, SCoV mRNAs, which have a 5' cap structure and 3' poly A tail like those of typical host mRNAs, were not susceptible to nsp1-mediated RNA cleavage and importantly, the presence of the 5'-end leader sequence protected the SCoV mRNAs from nsp1-induced endonucleolytic RNA cleavage. The escape of viral mRNAs from nsp1-induced RNA cleavage may be an important strategy by which the virus circumvents the action of nsp1 leading to the efficient accumulation of viral mRNAs and viral proteins during infection.

  15. Fracking, fracture, and permeability

    Science.gov (United States)

    Turcotte, D. L.; Norris, J.; Rundle, J. B.

    2013-12-01

    Injections of large volumes of water into tight shale reservoirs allows the extraction of oil and gas not previously accessible. This large volume 'super' fracking induces damage that allows the oil and/or gas to flow to an extraction well. The purpose of this paper is to provide a model for understanding super fracking. We assume that water is injected from a small spherical cavity into a homogeneous elastic medium. The high pressure of the injected water generates hoop stresses that reactivate natural fractures in the tight shales. These fractures migrate outward as water is added creating a spherical shell of damaged rock. The porosity associated with these fractures is equal to the water volume injected. We obtain an analytic expression for this volume. We apply our model to a typical tight shale reservoir and show that the predicted water volumes are in good agreement with the volumes used in super fracking.

  16. DEM Particle Fracture Model

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Boning [Univ. of Colorado, Boulder, CO (United States); Herbold, Eric B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Homel, Michael A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Regueiro, Richard A. [Univ. of Colorado, Boulder, CO (United States)

    2015-12-01

    An adaptive particle fracture model in poly-ellipsoidal Discrete Element Method is developed. The poly-ellipsoidal particle will break into several sub-poly-ellipsoids by Hoek-Brown fracture criterion based on continuum stress and the maximum tensile stress in contacts. Also Weibull theory is introduced to consider the statistics and size effects on particle strength. Finally, high strain-rate split Hopkinson pressure bar experiment of silica sand is simulated using this newly developed model. Comparisons with experiments show that our particle fracture model can capture the mechanical behavior of this experiment very well, both in stress-strain response and particle size redistribution. The effects of density and packings o the samples are also studied in numerical examples.

  17. Tibial shaft fracture

    DEFF Research Database (Denmark)

    Larsen, Peter

    The overall purpose of the present PhD thesis was to provide up-to-date information of the epidemiology of tibial shaft fractures and to investigate the development in quality of life, pain and functional outcomes from surgery and onwards, following a tibial shaft fracture treated with...... intramedullary nailing. Study I reported an incidence of 16.9/100,000/year from a complete population. Study II reported the long-term patient-reported outcomes and showed that approximately 8 years after the fracture patients reported significantly worse outcome for 4 of the 5 KOOS subscales compared to the...... IV also showed a significant worse outcome in 3 of the 5 KOOS subscales compared to a reference population at 12-months follow-up. Moreover, this study showed that increasing difference in muscle strength for knee extension between legs was associated with a decreasing QOL. The results of this thesis...

  18. Tibial Plateau Fractures

    DEFF Research Database (Denmark)

    Elsøe, Rasmus

    This PhD thesis reported an incidence of tibial plateau fractures of 10.3/100,000/year in a complete Danish regional population. The results reported that patients treated for a lateral tibial plateau fracture with bone tamp reduction and percutaneous screw fixation achieved a satisfactory level of...... radiological outcomes and a level of health related quality of life (Eq5d) below but not significantly different from the Danish reference population at a mean of 5.2 years follow-up. Furthermore, a knee injury-specific questionnaire (KOOS) reported a level of disability close to a reference population with...... only the subgroup Sport significantly below the age matched reference population. The thesis reports a level of health related quality of life (Eq5d) and disability (KOOS) significantly below established reference populations for patients with bicondylar tibial plateau fracture treated with a ring...

  19. Osteoporotic vertebral fractures: SPECT findings

    International Nuclear Information System (INIS)

    The purpose of this study was to evaluate the usefulness of single photon emission computed tomography (SPECT) of bone using Tc-99m MDP in the diagnosis of osteoporotic vertebral fractures. Thirty two patients with osteoporotic vertebral fracture were included in this study (mean age: 67±8, male: 5, female: 27). Seventy nine vertebral fractures were detected (38 thoracic/thoracolumbar lesions and 41 lumbar lesions), which were classified by type of deformity (wedge, biconcave or compression). The patterns and locations of increased uptakes were examined and analyzed. Forty seven wedge fractures, 20 biconcave fractures and 12 compression fractures were found. Diffuse and asymmetric uptakes were common in fractured bodies. More than one uptake were examined in 69 posterior elements of fractured vertebrae (87.3%) including 40 of 47 wedge fractures (85.1%), 17 of 20 biconcave fractures (85.0%) and 12 of 12 compression fractures (100%). Wedge fractures were predominant fracture in thoracic/thoracolumbar spine whereas incidence of biconcave or compression type was similar to that of wedge fracture in lumbar spine (p =0.04). Spinous process uptake was more frequently seen in lumbar lesions than thoracic/thoracolumbar lesions (p 0.009). Facet joint uptake in biconcave fracture was more common in lumbar spine (92.3%) than thoracic/thoracolumbar spine (57.1%). Spinous process uptake in biconcave fracture was also more frequently detected in lumbar spine (p = 0.043). Bone SPECT was useful in the evaluation of osteoporotic vertebral fracture, especially posterior elements of vertebrae

  20. Transstyloid, transscaphoid, transcapitate fracture: a variant of scaphocapitate fractures.

    LENUS (Irish Health Repository)

    Burke, Neil G

    2014-01-01

    Transstyloid, transscaphoid, transcapitate fractures are uncommon. We report the case of a 28-year-old man who sustained this fracture following direct trauma. The patient was successfully treated by open reduction internal fixation of the scaphoid and proximal capitate fragment, with a good clinical outcome at 1-year follow-up. This pattern is a new variant of scaphocapitate fracture as involves a fracture of the radial styloid as well.

  1. Effect of heat treatment on microstructure and fracture toughness of a V-5Cr-5Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.; Hamilton, M.L.; Jones, R.H. [Pacific Northwest Lab., Richland, WA (United States)

    1995-04-01

    The purpose of this research is to investigate the effect of heat treatment on microstructure and fracture toughness in the range of {minus}50 to 100{degrees}C for a V-5Cr-5Ti alloy. Fracture toughness and impact tests were performed on a V-5Cr-5Ti alloy. Specimens annealed at 1125{degree}C for 1 h and furnace cooled in a vacuum of 1.33 x 10{sup {minus}5} Pa were brittle at room temperature and experienced a mixture of intergranular and cleavage fracture. The ductile to brittle transition temperature was estimated to be about 20{degree}C. When some specimens were given an additional annealing at 890{degree}C for 24 h, they became very ductile at room temperature and fractured by microvoid coalescence.

  2. Effect of helium bubbles at grain boundaries on the fracture characteristics of high-density 238PuO2

    International Nuclear Information System (INIS)

    Helium bubbles that formed at grain boundaries in high density (greater than 92 percent of theoretical) 238PuO2 shards did not affect the room temperature fracture behavior as observed by scanning electron microscopy. Fracture was predominantly by brittle transgranular cleavage with only infrequent intergranular failure observed. Pores (approximately 5 μm dia) that formed within the grains during the sintering process, rather than helium bubbles, initiated fractures. Helium bubbles were observed occasionally on the fracture surfaces of 20-month-old shards that had been heated to 16000C for 8 h and subsequently crushed at room temperature. The average radius of these bubbles was approximately 1 μm. These bubbles were not interconnected, but were sometimes aligned in stringers

  3. Sealing of fractured rock

    International Nuclear Information System (INIS)

    This paper consists of a presentation of the third phase of the Stripa Project. This phase was dedicated to fracture sealing. First of all it has been necessary to show that fine-grained grouts could effectively be injected in relatively fine cracks, and that the fluidity of bentonite could also be enhanced. The field tests comprised investigation of excavation-induced disturbance and attempts to seal disturbed rock, and, in separate tests, grouting of deposition holes and a natural fine-fracture zone. (TEC). 12 figs., 1 tab., 6 refs

  4. Fractured Petroleum Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Firoozabadi, Dr. Abbas

    2000-01-18

    In this report the results of experiments of water injection in fractured porous media comprising a number of water-wet matrix blocks are reported for the first time. The blocks experience an advancing fracture-water level (FWL). Immersion-type experiments are performed for comparison; the dominant recovery mechanism changed from co-current to counter-current imbibition when the boundary conditions changed from advancing FWL to immersion-type. Single block experiments of co-current and counter-current imbibition was performed and co-current imbibition leads to more efficient recovery was found.

  5. Cleavage-based voting behavior in cross-national perspective : Evidence from six postwar democracies

    NARCIS (Netherlands)

    Brooks, Clem; Nieuwbeerta, Paul; Manza, Jeff

    2006-01-01

    We investigate trends and cross-national variation in the impact of class, religious, and gender cleavages on voting behavior in six advanced capitalist democracies in the postwar period. Earlier research on cleavage voting has been criticized for utilizing outdated ‘‘two-class’’ models of class str

  6. Cleavage-based voting behavior in cross-national perspective: evidence from six postwar democracies

    NARCIS (Netherlands)

    Brooks, Clem; Nieuwbeerta, Paul; Manza, Jeff

    2006-01-01

    We investigate trends and cross-national variation in the impact of class, religious, and gender cleavages on voting behavior in six advanced capitalist democracies in the postwar period. Earlier research on cleavage voting has been criticized for utilizing outdated “two-class” models of class struc

  7. Coronavirus 3CL(pro) proteinase cleavage sites: Possible relevance to SARS virus pathology

    DEFF Research Database (Denmark)

    Kiemer, Lars; Lund, Ole; Brunak, Søren;

    2004-01-01

    in proteins such as the cystic fibrosis transmembrane conductance regulator ( CFTR), transcription factors CREB-RP and OCT-I, and components of the ubiquitin pathway. Conclusions: Our prediction method NetCorona predicts coronavirus cleavage sites with high specificity and several potential cleavage...

  8. Inhibition of RecA-mediated cleavage in covalent dimers of UmuD.

    OpenAIRE

    Lee, M. H.; Guzzo, A; Walker, G C

    1996-01-01

    Disulfide-cross-linked UmuD2 derivatives were cleaved poorly upon incubation with activated RecA. Reducing the disulfide bonds prior to incubating the derivatives with RecA dramatically increased their extent of cleavage. These observations suggest that the UmuD monomer is a better substrate for the RecA-mediated cleavage reaction than the dimer.

  9. Unexpected tolerance of alpha-cleavage of the prion protein to sequence variations.

    Directory of Open Access Journals (Sweden)

    José B Oliveira-Martins

    Full Text Available The cellular form of the prion protein, PrP(C, undergoes extensive proteolysis at the alpha site (109K [see text]H110. Expression of non-cleavable PrP(C mutants in transgenic mice correlates with neurotoxicity, suggesting that alpha-cleavage is important for PrP(C physiology. To gain insights into the mechanisms of alpha-cleavage, we generated a library of PrP(C mutants with mutations in the region neighbouring the alpha-cleavage site. The prevalence of C1, the carboxy adduct of alpha-cleavage, was determined for each mutant. In cell lines of disparate origin, C1 prevalence was unaffected by variations in charge and hydrophobicity of the region neighbouring the alpha-cleavage site, and by substitutions of the residues in the palindrome that flanks this site. Instead, alpha-cleavage was size-dependently impaired by deletions within the domain 106-119. Almost no cleavage was observed upon full deletion of this domain. These results suggest that alpha-cleavage is executed by an alpha-PrPase whose activity, despite surprisingly limited sequence specificity, is dependent on the size of the central region of PrP(C.

  10. Ischiopubic insufficiency fractures: MRI appearances

    International Nuclear Information System (INIS)

    Objective. To evaluate the MRI appearances in insufficiency fractures. Design. A retrospective analysis of spin echo MR images with gadolinium-enhancement was undertaken with the emphasis on the signal change and the shape of the fracture gap and the adjacent bone marrow. Patients. Five elderly women who had ischiopubic insufficiency fractures (pubis, 4; ischium 1) underwent MRI to exclude the possibility of pathologic fractures. Results and conclusions. In no case was contrast enhancement noted at the fracture gap or the adjacent bone marrow, but a cleft-life, elongated bright signal area suggesting ''fluid collection'' was noted within the fracture gap. Absence of contrast enhancement and ''fluid collection'' at the fracture gap might suggest nonunion of a fracture, which is additional information provided only by MRI. (orig.)

  11. Progressive Fracture of Composite Structures

    Science.gov (United States)

    Chamis, Christos C.; Minnetyan, Levon

    2008-01-01

    A new approach is described for evaluating fracture in composite structures. This approach is independent of classical fracture mechanics parameters like fracture toughness. It relies on computational simulation and is programmed in a stand-alone integrated computer code. It is multiscale, multifunctional because it includes composite mechanics for the composite behavior and finite element analysis for predicting the structural response. It contains seven modules; layered composite mechanics (micro, macro, laminate), finite element, updating scheme, local fracture, global fracture, stress based failure modes, and fracture progression. The computer code is called CODSTRAN (Composite Durability Structural ANalysis). It is used in the present paper to evaluate the global fracture of four composite shell problems and one composite built-up structure. Results show that the composite shells and the built-up composite structure global fracture are enhanced when internal pressure is combined with shear loads.

  12. Stress fractures in young athletes.

    Science.gov (United States)

    Orava, S; Jormakka, E; Hulkko, A

    1981-01-01

    In a series of 16 cases of stress fractures in 15-year-old and younger athletes 8 fractures occurred in boys and 8 in girls. There were no differences between the sexes in the athletes' training habits. Ten of the fractures were located at the tibia, seven at its upper third and three at the lower part of the bone. Three fractures were found in the fibula, in the metatarsal bones two stress fractures and in the femur one stress fracture. Most stress fractures were caused by endurance type sports. The daily training distances were not particularly high at the time of the onset of the symptoms. In most cases the diagnosis was based on a radiological evaluation. A sufficiently long pause from all athletic activity was enough treatment. Stress fractures in children are very uncommon. PMID:7295000

  13. Structure-Property-Fracture Mechanism Correlation in Heat-Affected Zone of X100 Ferrite-Bainite Pipeline Steel

    Science.gov (United States)

    Li, Xueda; Ma, Xiaoping; Subramanian, S. V.; Misra, R. D. K.; Shang, Chengjia

    2015-03-01

    Structural performance of a weld joint primarily depends on the microstructural characteristics of heat-affected zone (HAZ). In this regard, the HAZ in X100 ferrite-bainite pipeline steel was studied by separating the HAZ into intercritically reheated coarse-grained (ICCG) HAZ containing and non-containing regions. These two regions were individually evaluated for Charpy impact toughness and characterized by electron back-scattered diffraction (EBSD). Low toughness of ~50 J was obtained when the notch of impact specimen encountered ICCGHAZ and high toughness of ~180 J when the notch did not contain ICCGHAZ. Fracture surface was ~60 pct brittle in the absence of ICCGHAZ, and 95 pct brittle (excluding shear lip) in the presence of ICCGHAZ in the impact tested samples. The underlying reason is the microstructure of ICCGHAZ consisted of granular bainite and upper bainite with necklace-type martensite-austenite (M-A) constituent along grain boundaries. The presence of necklace-type M-A constituent notably increases the susceptibility of cleavage microcrack nucleation. ICCGHAZ was found to be both the initiation site of the whole fracture and cleavage facet initiation site during brittle fracture propagation stage. Furthermore, the study of secondary microcracks beneath CGHAZ and ICCGHAZ through EBSD suggested that the fracture mechanism changes from nucleation-controlled in CGHAZ to propagation-controlled in ICCGHAZ because of the presence of necklace-type M-A constituent in ICCGHAZ. Both fracture mechanisms contribute to the poor toughness of the sample contained ICCGHAZ.

  14. Effect of Zn content on microstructure,mechanical properties and fracture behavior of Mg-Mn alloy

    Directory of Open Access Journals (Sweden)

    Yin Dongsong

    2009-02-01

    Full Text Available The optical microscope, scanning electron microscope and universal testing machine are used to investigate the effect of Zn content on the microstructure, mechanical properties and fracture behavior of Mg-Mn-Zn alloy. The results indicate that fi ne (Mg, Mn, Al-containing phases are distributed uniformly in the Mg-Mn alloy matrix, while small amount of (Mg, Zn-containing phases are formed in the matrix and the grain boundary becomes coarse when 1wt.% Zn is added. As the Zn content increases, the amount of (Mg, Zn-containing phases increases, and the grain boundary becomes coarser. When the Zn content is between 3wt.%-5wt.%, slender (Mg, Zn-containing phases precipitate at the grain boundary. The addition of Zn could reduce the grain size and enhance the mechanical properties of the alloy matrix, and both of the effects can be enhanced by increasing the Zn content further more. When the Zn content is more than 3wt.%, grain size stops decrease, the strength cannot be improved any more and elongation decreases significantly. The fracture behavior of Mg-Mn alloy appears to be cleavage fracture, and transforms into quasi-cleavage fracture as Zn is added. When Zn content exceeded 3wt.%, large amount of (Mg, Zn-containing phases appear on the fracture face, and act as the crack sources.

  15. Ultrasensitive monitoring of ribozyme cleavage product using molecular-beacon-ligation system

    Institute of Scientific and Technical Information of China (English)

    MENG XiangXian; TANG ZhiWen; WANG KeMin; TAN WeiHong; YANG XiaoHai; LI Jun; GUO QiuPing

    2007-01-01

    This paper reports a new approach to detect ribozyme cleavage product based on the molecular- beacon-ligation system. The molecular beacon, designed in such a way that one-half of its loop is complementary to ribozyme cleavage product, is used to monitor ligation process of RNA/DNA complex in a homogeneous solution and to convert directly cleavage product information into fluorescence signal. The method need not label ribozyme and ribozyme substrate, which is fast, simple and ultrasensitive for detection of cleavage product. Detection limit of the assay is 0.05 nmol/L. The cleavage product of hammerhead ribozyme against hepatitis C virus RNA (HCV-RNA) was detected perfectly based on this assay. Owing to its ultrasensitivity, excellent specificity, convenience and fidelity, this method might hold out great promise in ribozyme reaction and ribozyme gene therapy.

  16. Impacted Teeth and Mandibular Fracture

    OpenAIRE

    Metin, Murat; Şener, İsmail; Tek, Mustafa

    2007-01-01

    Objectives In this retrospective study, we measured the relationship between the presences of impacted or unerupted teeth in the mandible and mandibular fractures. Methods The records and radiographs of 41 patients with mandibular fracture associated with impacted or unerupted teeth were examined. The presence of impacted or unerupted teeth were assessed for each patient and related to the occurrence of fractures of mandible. Results Patients with fracture in the impacted or unerupted teeth a...

  17. Management of osteoporotic vertebral fractures

    Directory of Open Access Journals (Sweden)

    Yannis Dionyssiotis

    2010-06-01

    Full Text Available Yannis DionyssiotisRhodes General Hospital, Rhodes, GreeceAbstract: Osteoporotic vertebral fractures are associated with considerable reduction of quality of life, morbidity, and mortality. The management of patients with vertebral fractures should include treatment for osteoporosis and measures to reduce pain and improve mobility. This article provides information for management and rehabilitation of vertebral fractures based on clinical experience and literature.Keywords: vertebral fracture, quality of life, rehabilitation, osteoporosis

  18. Complications in Ankle Fracture Surgery

    OpenAIRE

    Ovaska, Mikko

    2014-01-01

    Mikko Ovaska. Complications in Ankle Fracture Surgery. Helsinki Bone and Joint Research Group, Department of Orthopaedic Surgery and Traumatology, Faculty of Medicine, University of Helsinki, Finland. Helsinki 2014. Ankle fractures are among the most frequently encountered surgically treated fractures. The operative treatment of this fracture may be associated with several complications. The most frequently encountered complications are related wound healing, and deep infection may have d...

  19. Fracture toughness testing of V-4Cr-4Ti at 25{degrees}C and -196{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.X.; Kurtz, R.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    Measurements of the fracture toughness of the production-scale heat (832665) of V-4Cr-4Ti have been performed at 25{degrees}C and {minus}196{degrees}C using compact tension (CT) specimens. Test specimens were vacuum annealed at either 1000{degrees}C for 1 hour (HT1) or 1050{degrees}C for two hours (HT2). Specimens given the HT1 treatment were annealed after final machining, whereas the HT2 specimens received the 1050{degrees}C anneal at Teledyne Wah Chang prior to final machining. Following machining HT2 specimens were then vacuum annealed at 180{degrees}C for two hours to remove hydrogen. Specimens treated using HT1 had a partially recrystallized microstructure and those treated using HT2 had a fully recrystallized microstructure. The fracture toughness at 25{degrees}C was determined by J-integral tests and at {minus}196{degrees}C by ASTM E 399 type tests. Toughness values obtained at {minus}196{degrees}C were converted to J-integral values for comparison to the 25{degrees}C data. The 25{degrees}C fracture toughness was very high with none of the specimens giving valid results per ASTM criteria. Specimens fractured by microvoid coalescence. The fracture toughness at {minus}196{degrees}C was much lower than that at 25{degrees}C and the fracture surface showed predominantly cleavage features. The present results show a transition from ductile to brittle behavior with decreasing test temperature which is not observed from one-third scale Charpy impact tests. The fracture toughness at {minus}196{degrees}C was still quite high, however, at about 75 kJ/m{sup 2}. Delaminations in planes normal to the thickness direction were seen at both test temperatures. Fracture surfaces inside the delaminations exhibited nearly 100% cleavage facets. The cause of the brittle delaminations was not determined, but will be a subject for further investigation.

  20. Numerical Modeling of Fracture Propagation in Naturally Fractured Formations

    Science.gov (United States)

    Wang, W.; Prodanovic, M.; Olson, J. E.; Schultz, R.

    2015-12-01

    Hydraulic fracturing consists of injecting fluid at high pressure and high flowrate to the wellbore for the purpose of enhancing production by generating a complex fracture network. Both tensile failure and shear failure occur during the hydraulic fracturing treatment. The shear event can be caused by slip on existing weak planes such as faults or natural fractures. From core observation, partially cemented and fully cemented opening mode natural fractures, often with considerable thickness are widely present. Hydraulic fractures can propagate either within the natural fracture (tensile failure) or along the interface between the natural fracture and the rock matrix (tensile/shear failure), depending on the relative strength of cement and rock matrix materials, the bonding strength of interface, as well as the presence of any heterogeneities. In this study, we evaluate the fracture propagation both experimentally and numerically. We embed one or multiple inclusions of different mechanical properties within synthetic hydrostone samples in order to mimic cemented natural fractures and rock. A semi-circular bending test is performed for each set of properties. A finite element model built with ABAQUS is used to mimic the semi-circular bending test and study the fracture propagation path, as well as the matrix-inclusion bonding interface status. Mechanical properties required for the numerical model are measured experimentally. The results indicate that the match between experiment and modeling fracture path are extremely sensitive to the chosen interface (bonding) model and related parameters. The semi-circular bending test is dry and easily conducted, providing a good platform for validating numerical approaches. A validated numerical model will enable us to add pressurized fluid within the crack and simulate hydraulic fracture-natural fracture interaction in the reservoir conditions, ultimately providing insights into the extent of the fracture network.

  1. Applicability of smaller than Charpy specimens for fracture toughness characterization with the VTT method

    International Nuclear Information System (INIS)

    The term fracture toughness usually refers to the linear elastic fracture resistance parameter KIC. In the case of structural steels, the estimation of KIC is limited to the lower shelf of toughness or require extremely large specimens. This specimen size requirement has been one major obstacle for applying fracture mechanics in structural integrity assessment outside aviation, nuclear and off-shore industries. During the last decade, a statistical data treatment methodology, based on a micro-mechanistic cleavage fracture model, combined with elastic plastic finite element analysis has enabled the fracture toughness to be characterized with small specimens in the ductile-to-brittle transition region. The methodology is known as the VTT method or the Master Curve procedure. The development has led to a new testing standard for fracture toughness testing of ferritic steels in the transition range. Here, the premises for the methodology are described and its validity range is discussed. Presently the methodology has been validated for as small as 10.10 mm2 bend specimens, but the use of even smaller specimens is under investigation. Specifically, results obtained with three different sub-Charpy specimen configurations are presented and discussed. (author)

  2. Application of fracture toughness scaling models to the ductile-to- brittle transition

    International Nuclear Information System (INIS)

    An experimental investigation of fracture toughness in the ductile-brittle transition range was conducted. A large number of ASTM A533, Grade B steel, bend and tension specimens with varying crack lengths were tested throughout the transition region. Cleavage fracture toughness scaling models were utilized to correct the data for the loss of constraint in short crack specimens and tension geometries. The toughness scaling models were effective in reducing the scatter in the data, but tended to over-correct the results for the short crack bend specimens. A proposed ASTM Test Practice for Fracture Toughness in the Transition Range, which employs a master curve concept, was applied to the results. The proposed master curve over predicted the fracture toughness in the mid-transition and a modified master curve was developed that more accurately modeled the transition behavior of the material. Finally, the modified master curve and the fracture toughness scaling models were combined to predict the as-measured fracture toughness of the short crack bend and the tension specimens. It was shown that when the scaling models over correct the data for loss of constraint, they can also lead to non-conservative estimates of the increase in toughness for low constraint geometries

  3. Fracture behavior of W based materials

    International Nuclear Information System (INIS)

    This report describes the results of a program to investigate the fracture properties of tungsten based materials. In particular, the role of crack velocity on crack instability was determined in a W-Fe-Ni-Co ''heavy alloy'' and pure polycrystalline tungsten. A considerable effort was expended on the development of an appropriate crack velocity gage for use on these materials. Having succeeded in that, the gage technology was employed to determine the crack velocity response to the applied level of stress intensity factor at the onset of crack instability in pre-cracked specimens. The results were also correlated to the failure mode observed in two material systems of interest. Major results include: (1) unstable crack velocity measurements on metallic specimens which require high spatial resolution require the use of brittle, insulating substrates, as opposed to the ductile, polymer based substrates employed in low spatial resolution measurements; and (2) brittle failure modes, such as cleavage, are characterized by relatively slow unstable crack velocities while evidence of high degrees of deformation are associated with failures which proceed at high unstable crack velocities. This latter behavior is consistent with the predictions of the modeling of Hack et al and may have a significant impact on the interpretation of fractographs in general

  4. Microcracks and Overpressure- Induced Fractures

    Institute of Scientific and Technical Information of China (English)

    Ahmed M. Al - QAHTANI

    2001-01-01

    The microfractures and natural fractures studies have a great significance in the hydrocarbon accumulation exploration and can be a good supporter for wide geophysical study on the major structures. This paper is a brief review on microcracks and overpressure- induced fracture. It is to discuss different views on the mechanism of fractures in the subsurface of the earth.

  5. Fatigue, degradation, and fracture 1990

    Energy Technology Data Exchange (ETDEWEB)

    Bamford, W.H. (Westinghouse Energy Systems (US)); Becht, C. IV (Becht Engineering Co., Inc. (US)); Bhandari, S. (Framatome (FR)); Gilman, J.D. (Electric Power Research Institute (US)); James, L.A. (Westinghouse Bettis Laboratory (US)); Prager, M. (Materials Properties Council (US))

    1990-01-01

    This book contains papers presented at the 1990 Pressure Vessels and Piping Conference. It is organized under the following headings: Environmental fatigue crack growth; Fatigue analysis and fracture assessment; Fatigue and fracture of piping; Fatigue and fracture of vessels; Degradation of ferritic, austenitic, and duplex stainless alloys in nuclear service.

  6. Fracture assessment of shallow-flaw cruciform beams tested under uniaxial and biaxial loading conditions

    International Nuclear Information System (INIS)

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate with the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states. (orig.)

  7. Upper tibial hyperextension fractures in infants: another occult toddler's fracture

    International Nuclear Information System (INIS)

    We describe the radiographic findings associated with occult upper tibial fractures in infants and young children and offer an explanation for the underlying mechanism from which they result. These fractures tend to be subtle, just as the classic spiral tibial fracture originally described by Dunbar et al. (1964, J Can Assoc Radiol 15: 136-144). The fracture we describe results from a hyperextension injury to the knee, and the knowledge of the mechanism of injury, the subtle radiographic findings, and the findings on physical examination allow one to diagnose this fracture with confidence. Otherwise, it easily can go undetected. (orig.)

  8. Elastic nails for fibular fracture in adult tibiofibular fractures.

    Science.gov (United States)

    Wang, Qiang; Xu, Hong-Guang; Zhang, Yin-Chang; Dong, Li-Jun

    2015-01-01

    Treatment of adult tibiofibular fractures, especially severely comminuted fractures, is technically challenging due to the lack of reduction markers and difficulty in restoring the alignment. Fixation of the fibula can facilitate reduction of the tibia fracture and restoration of the lower-extremity alignment. However, there are few literatures mentioned using intramedullary nail fixation for fibular fractures. Twenty-three cases of tibiofibular fractures were treated with elastic nails fixation fibular fractures and intramedullary nail or plate stabilization tibial fractures between January 2012 and December 2012. Adult tibiofibular fractures with fibular neck fractures or fibular fracture line apart from the ankle joint surface within 8 cm was ruled out. There were 19 males and 4 females with an average age of 41 years (range, 21-59 years). The injury causes included 11 falls and 12 traffic accidents. The left side was involved in 11 cases and the right side was involved in 12 cases. Seventeen cases were closed fractures and 6 cases were open fractures, all were Gustilo type I and II fractures. According to the AO classification, six fractures were defined as type 42A, 11 as type 42B, and 6 as type 42C. The average interval between injury and surgery was 5.8 d (range, 3-22 d). The operation time of elastic nails fixation fibular fractures was 24 minutes (range, 15-42 minutes). Primary wound healing was achieved in all patients. No complications such as infection and wound necrosis occurred. Twenty-one patients were followed up for a mean follow-up period of 16.3 months (range, 12-26 months). The mean duration of fracture healing in the radiographs was 4.1 months (range, 3-8 months). No recurrent fracture dislocation and breakage of implant were observed. At the last follow-up visit, the lower-extremity alignment was excellent. Two degrees of varus deformity was found in 3 cases, and 2 degrees of valgus deformity was observed in 2 cases, but there were no serious

  9. Neglected hangman fracture

    Directory of Open Access Journals (Sweden)

    Sudhir Kumar Srivastava

    2015-01-01

    Full Text Available Acute management of hangman fracture is well described; however the surgical management of neglected hangman fracture has not been described in literature. We report the surgical management of an untreated hangman′s fracture. A 30-year-old male had fallen from a tree 12 weeks back. Patient presented with cervical myelopathy and restricted neck movements. Radiographs and computed tomography (CT scan revealed fracture of pars interarticularis of axis with Grade III C2-C3 spondylolisthesis with localized kyphosis of 33°. Gentle reduction under general anesthesia (GA failed to improve the alignment. Patient was operated in three stages in a single setting. In Stage I, release of contracted anterior structures and C2-C3 discectomy was done in supine position followed by C2-C3 posterior fixation and fusion in Stage II. C2-C3 interbody bone grafting and anterior plating completed the third stage. C2-C3 interbody fusion was seen at 5 months and a CT scan at 18 months postoperative confirmed fusion and maintenance of alignment. The satisfactory outcome in our patient leads us to believe that anterior-posterior-anterior is the appropriate surgical approach for treatment of such patients.

  10. Oblique Axis Body Fracture

    DEFF Research Database (Denmark)

    Takai, Hirokazu; Konstantinidis, Lukas; Schmal, Hagen;

    2016-01-01

    type" fracture pattern. The first patient was treated conservatively with cervical spine immobilization in a semirigid collar. However, gross displacement was noted at the 6-week follow-up visit. The second patient was therefore treated operatively by C1-C3/4 posterior fusion and the course was...

  11. Fracturing rigid materials.

    Science.gov (United States)

    Bao, Zhaosheng; Hong, Jeong-Mo; Teran, Joseph; Fedkiw, Ronald

    2007-01-01

    We propose a novel approach to fracturing (and denting) brittle materials. To avoid the computational burden imposed by the stringent time step restrictions of explicit methods or with solving nonlinear systems of equations for implicit methods, we treat the material as a fully rigid body in the limit of infinite stiffness. In addition to a triangulated surface mesh and level set volume for collisions, each rigid body is outfitted with a tetrahedral mesh upon which finite element analysis can be carried out to provide a stress map for fracture criteria. We demonstrate that the commonly used stress criteria can lead to arbitrary fracture (especially for stiff materials) and instead propose the notion of a time averaged stress directly into the FEM analysis. When objects fracture, the virtual node algorithm provides new triangle and tetrahedral meshes in a straightforward and robust fashion. Although each new rigid body can be rasterized to obtain a new level set, small shards can be difficult to accurately resolve. Therefore, we propose a novel collision handling technique for treating both rigid bodies and rigid body thin shells represented by only a triangle mesh. PMID:17218752

  12. Fracture of articular cartilage.

    Science.gov (United States)

    Chin-Purcell, M V; Lewis, J L

    1996-11-01

    Crack formation and propagation is a significant element of the degeneration process in articular cartilage. In order to understand this process, and separate the relative importance of structural overload and material failure, methods for measuring the fracture toughness of cartilage are needed. In this paper, two such methods are described and used to measure fracture properties of cartilage from the canine patella. A modified single edge notch (MSEN) specimen was used to measure J, and a trouser tear test was used to measure T, both measures of fracture toughness with units of kN/m. A pseudo-elastic modulus was also obtained from the MSEN test. Several potential error sources were examined, and results for the MSEN test compared with another method for measuring the fracture parameter for urethane rubber. Good agreement was found. The two test methods were used to measure properties of cartilage from the patellae of 12 canines: 4-9 specimens from each of 12 patellae, with 5 right-left pairs were tested. Values of J ranged from 0.14-1.2 kN/m. J values correlated with T and were an average of 1.7 times larger than T. A variety of failure responses was seen in the MSEN tests, consequently a grade of 0 to 3 was assigned to each test, where 0 represented a brittle-like crack with minimal opening and 3 represented plastic flow with no crack formation. The initial cracks in 12/82 specimens did not propagate and were assigned to grade 3. The method for reducing data in the MSEN test assumed pseudo-elastic response and could not be used for the grade 3 specimens. Stiffness did not correlate with J. Neither J nor T was statistically different between right-left pairs, but varied between animals. The test methods appear useful for providing a quantitative measure of fracture toughness for cartilage and other soft materials. PMID:8950659

  13. Sealing of rock fractures

    International Nuclear Information System (INIS)

    The major water-bearing fractures in granite usually from fairly regular sets but the extension and degree of connectivity is varying. This means that only a few fractures that are interconnected with the deposition holes and larger water-bearing structures in a HLW repository are expected and if they can be identified and cut off through sealing it would be possible to improve the isolation of waste packages very effectively. Nature's own fracture sealing mechanisms may be simulated and a survey of the involved processes actually suggests a number of possible filling methods and substances. Most of them require high temperature and pressure and correspondingly sophisticated techniques, but some are of potential interest for immediate application with rather moderate effort. Such a technique is to fill the fractures with clayey substances which stay flexible and low-permeable provided that they remain physically and chemically intact. It is demonstrated in the report that effective grouting requires a very low viscosity and shear strength of the substance and this can be achieved by mechanical agitation as demonstrated in this report. Thus, by superimposing static pressure and shear waves induced by percussion hammering at a suitable frequency, clays and fine-grained silts as well as cement can be driven into fractures with an average aperture as small as 0.1 mm. Experiments were made in the laboratory using concrete and steel plates, and a field pilot test was also conducted under realistic conditions on site in Stripa. They all demonstrated the practicality of the 'dynamic injection technique' and that the fluid condition of the grouts yielded complete filling of the injected space to a considerable distance from the injection point. The field test indicated a good sealing ability as well as a surprisingly high resistance to erosion and piping. (author)

  14. Structural and functional basis for RNA cleavage by Ire1

    Directory of Open Access Journals (Sweden)

    Stroud Robert M

    2011-07-01

    Full Text Available Abstract Background The unfolded protein response (UPR controls the protein folding capacity of the endoplasmic reticulum (ER. Central to this signaling pathway is the ER-resident bifunctional transmembrane kinase/endoribonuclease Ire1. The endoribonuclease (RNase domain of Ire1 initiates a non-conventional mRNA splicing reaction, leading to the production of a transcription factor that controls UPR target genes. The mRNA splicing reaction is an obligatory step of Ire1 signaling, yet its mechanism has remained poorly understood due to the absence of substrate-bound crystal structures of Ire1, the lack of structural similarity between Ire1 and other RNases, and a scarcity of quantitative enzymological data. Here, we experimentally define the active site of Ire1 RNase and quantitatively evaluate the contribution of the key active site residues to catalysis. Results This analysis and two new crystal structures suggest that Ire1 RNase uses histidine H1061 and tyrosine Y1043 as the general acid-general base pair contributing ≥ 7.6 kcal/mol and 1.4 kcal/mol to transition state stabilization, respectively, and asparagine N1057 and arginine R1056 for coordination of the scissile phosphate. Investigation of the stem-loop recognition revealed that additionally to the stem-loops derived from the classic Ire1 substrates HAC1 and Xbp1 mRNA, Ire1 can site-specifically and rapidly cleave anticodon stem-loop (ASL of unmodified tRNAPhe, extending known substrate specificity of Ire1 RNase. Conclusions Our data define the catalytic center of Ire1 RNase and suggest a mechanism of RNA cleavage: each RNase monomer apparently contains a separate catalytic apparatus for RNA cleavage, whereas two RNase subunits contribute to RNA stem-loop docking. Conservation of the key residues among Ire1 homologues suggests that the mechanism elucidated here for yeast Ire1 applies to Ire1 in metazoan cells, and to the only known Ire1 homologue RNase L.

  15. SENILE OSTEOPOROSIS AND HIP FRACTURE

    Institute of Scientific and Technical Information of China (English)

    戴力扬

    1995-01-01

    A randomized block design was used to compare the Singh index, the cortical index of the femoral neck and the lateral cortical width of the femur of a group of patients with femoral neck fracture, a group with intertrochanterie fracture, and a normal contrrol group among a total of 102 postmenopausal women. The three irtdiees in fracture grotlp were very significantly (P<0. 01) or significantly (P<0. 05) different from those in the normal control subjects. The importance of osteopomosis in hip fracture of the aged is con-firmed. Radiographic measurement of bone mass was found to have some predictive value for the risk of hip fracture.

  16. Seismic characterization of fracture properties

    International Nuclear Information System (INIS)

    The purpose of this paper is to show that there is a relationship, both empirical and theoretical, between the measured seismic response, the mechanical stiffness (also referred to as specific stiffness) of fractures and their hydraulic conductivity. Laboratory measurements of the mechanical stiffness, hydraulic conductivity and seismic properties of natural fractures are summarized. A theoretical model for the amplitude and group time delay for compressional and shear waves transmitted across a single fracture is presented. Predictions based on this model are compared with laboratory measurements. Finally, the results for a single fracture are extended to multiple parallel fractures. 13 refs., 6 figs

  17. Extension of microwave-accelerated residue-specific acid cleavage to proteins with carbohydrate side chains and disulfide linkages

    OpenAIRE

    Li, Jinxi; Shefcheck, Kevin; Callahan, John; Fenselau, Catherine

    2008-01-01

    This laboratory has introduced a chemical method for residue-specific protein cleavage and has provided a preliminary assessment of the suitability of microwave accelerated acid cleavage as a proteomic tool. This report is a continuing assessment of the fate of common protein modifications in microwave-accelerated acid cleavage. We have examined the cleavage of ribonuclease A and the related N-linked glycoprotein ribonuclease B, and the O-linked glycoprotein alpha crystallin A chain, using MA...

  18. Not all social cleavages are the same: On the relationship between religious diversity and party system fragmentation

    OpenAIRE

    Raymond, Christopher D.

    2016-01-01

    Most studies examining the relationship between social cleavages and party system fragmentation maintain that higher levels of social diversity lead to greater party system fragmentation. However, most aggregate-level studies focus on one type of social cleavage:ethnic diversity. In order to develop a better understanding of how different cleavages impact electoral competition, this paper considers another type of social cleavage: religious diversity.Contrary to previous literature, higher le...

  19. Party agency and the religious-secular cleavage in post-Communist countries: The case of Romania

    OpenAIRE

    Raymond, Christopher

    2014-01-01

    Research focusing on several post-communist countries has found evidence of social cleavage effects on political behaviour similar to those found in Western Europe. In some post-communist countries, however, social cleavage effects appear far weaker (if at all). To understand why this is the case, I perform a case study of Romania, focusing on the religious–secular cleavage. Drawing upon research that emphasises the role of parties in forming cleavages, I argue that the reason for the absence...

  20. Fusion function of the Semliki Forest virus spike is activated by proteolytic cleavage of the envelope glycoprotein precursor p62.

    OpenAIRE

    Lobigs, M; Garoff, H

    1990-01-01

    The precursor protein p62 of the prototype alphavirus Semliki Forest virus (SFV) undergoes during transport to the cell surface a proteolytic cleavage to form the mature envelope glycoprotein E2. To investigate the biological significance of this cleavage event, single amino acid substitutions were introduced at the cleavages site through mutagenesis of cDNA corresponding to the structural region of the SFV genome. The phenotypes of the cleavage site mutants were studied in BHK cells by using...

  1. Modulation of enteroviral proteinase cleavage of poly(A)-binding protein (PABP) by conformation and PABP-associated factors

    OpenAIRE

    Rivera, Carlos I.; Lloyd, Richard E.

    2008-01-01

    Poliovirus (PV) causes a drastic inhibition of cellular cap-dependant protein synthesis due to the cleavage of translation factors eukaryotic initiation factor 4G (eIF4G) and poly (A) binding protein (PABP). Only about half of cellular PABP is cleaved by viral 2A and 3C proteinases during infection. We have investigated PABP cleavage determinants that regulate this partial cleavage. PABP cleavage kinetics analyses indicate that PABP exists in multiple conformations, some of which are resistan...

  2. Pubic insufficiency fracture: MRI findings

    International Nuclear Information System (INIS)

    To evaluate the characteristic MRI findings of pubic insufficiency fracture. In nine cases of pubic insufficiency fracture, the findings of plain radiography (n=9), MRI (n=9), and bone scintigraphy (n=8) were reviewed. We retrospectively analyzed, with regard to fracture site, the destructive pattern revealed by plain radiography, and uptake by other pelvic bones, as demonstrated by RI bone scanning. The MR findings evaluated were the fracture gap and its signal intensity, the site and signal intensity of the soft tissue mass, and other pelvic bone fractures. Plain radiography revealed osteolysis and sclerosis of pubic bone in eight of nine cases (89%), and parasymphyseal fractures in seven (78%). RI indicated uptake by the sacrum in six cases (66%), and by the ilium in three (33%). MR findings of fracture gap (seven cases, 78%) were hypo to isointensity on T1WI, hyper intensity on T2WI and the absence of contrast enhancement. Soft tissue masses were found in seven cases (78%); in four of these the location was parasymphyseal, and in three, surrounding muscle was involved. Hypo to isointensity was revealed by T1WI, hyperintensity by T2WI, and there was peripheral enhancement. Other associated pelvic bone fractures involved the sacrum in seven cases and the ilium in four. The characteristic MR findings of pubic insufficiency fracture were parasymphyseal location, fracture gap, peripherally enhanced soft tissue mass formation, and fractures of other pelvic bones, namely the sacrum and ilium

  3. Pubic insufficiency fracture: MRI findings

    Energy Technology Data Exchange (ETDEWEB)

    Min, Tae Kyu; Lee, Yeon Soo; Park, Jeong Mi; Kim, Jee Young; Chung, Hong Jun; Lee, Eun Hee; Lee, Eun Ja; Kang, So Won [College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of); Han Tae Il [Eulji Medical College, Taejon (Korea, Republic of)

    2000-10-01

    To evaluate the characteristic MRI findings of pubic insufficiency fracture. In nine cases of pubic insufficiency fracture, the findings of plain radiography (n=9), MRI (n=9), and bone scintigraphy (n=8) were reviewed. We retrospectively analyzed, with regard to fracture site, the destructive pattern revealed by plain radiography, and uptake by other pelvic bones, as demonstrated by RI bone scanning. The MR findings evaluated were the fracture gap and its signal intensity, the site and signal intensity of the soft tissue mass, and other pelvic bone fractures. Plain radiography revealed osteolysis and sclerosis of pubic bone in eight of nine cases (89%), and parasymphyseal fractures in seven (78%). RI indicated uptake by the sacrum in six cases (66%), and by the ilium in three (33%). MR findings of fracture gap (seven cases, 78%) were hypo to isointensity on T1WI, hyper intensity on T2WI and the absence of contrast enhancement. Soft tissue masses were found in seven cases (78%); in four of these the location was parasymphyseal, and in three, surrounding muscle was involved. Hypo to isointensity was revealed by T1WI, hyperintensity by T2WI, and there was peripheral enhancement. Other associated pelvic bone fractures involved the sacrum in seven cases and the ilium in four. The characteristic MR findings of pubic insufficiency fracture were parasymphyseal location, fracture gap, peripherally enhanced soft tissue mass formation, and fractures of other pelvic bones, namely the sacrum and ilium.

  4. Local approach of cleavage fracture applied to a vessel with subclad flaw. A benchmark on computational simulation

    International Nuclear Information System (INIS)

    A benchmark on the computational simulation of a cladded vessel with a 6.2 mm sub-clad flaw submitted to a thermal transient has been conducted. Two-dimensional elastic and elastic-plastic finite element computations of the vessel have been performed by the different partners with respective finite element codes ASTER (EDF), CASTEM 2000 (CEA), SYSTUS (Framatome) and ABAQUS (AEA Technology). Main results have been compared: temperature field in the vessel, crack opening, opening stress at crack tips, stress intensity factor in cladding and base metal, Weibull stress σw and probability of failure in base metal, void growth rate R/R0 in cladding. This comparison shows an excellent agreement on main results, in particular on results obtained with local approach. (K.A.)

  5. Excess mortality following hip fracture

    DEFF Research Database (Denmark)

    Abrahamsen, B; van Staa, T; Ariely, R;

    2009-01-01

    Summary This systematic literature review has shown that patients experiencing hip fracture after low-impact trauma are at considerable excess risk for death compared with nonhip fracture/community control populations. The increased mortality risk may persist for several years thereafter......, highlighting the need for interventions to reduce this risk.Patients experiencing hip fracture after low-impact trauma are at considerable risk for subsequent osteoporotic fractures and premature death. We conducted a systematic review of the literature to identify all studies that reported unadjusted and...... excess mortality rates for hip fracture. Although a lack of consistent study design precluded any formal meta-analysis or pooled analysis of the data, we have shown that hip fracture is associated with excess mortality (over and above mortality rates in nonhip fracture/community control populations...

  6. Irreversible and reversible topoisomerase II DNA cleavage stimulated by clerocidin: sequence specificity and structural drug determinants.

    Science.gov (United States)

    Binaschi, M; Zagotto, G; Palumbo, M; Zunino, F; Farinosi, R; Capranico, G

    1997-05-01

    In contrast to other topoisomerase II poisons, the microbial terpenoid clerocidin was shown to stimulate irreversible topoisomerase II-mediated DNA cleavage. To establish the structural determinants for drug activity, in this study we have investigated intensity patterns and sequence specificity of clerocidin-stimulated DNA cleavage using 5'-end 32P-labeled DNA fragments. At a majority of the sites, clerocidin-stimulated cleavage did not revert upon NaCl addition; nevertheless, at some sites, cleavage completely reverted. Statistical analyses showed that drug-preferred bases were different in the two cases: guanine and cytosine were highly preferred at position -1 at irreversible and reversible sites, respectively. These results demonstrated that cleavage irreversibility was site selective and required a guanine at the 3' end of the cut. Further experiments revealed that some irreversible sites showed an abnormal electrophoretic mobility in sequencing gels with respect to cleaved bands generated by 4-(9-acridinylamino)methanesulfon-m-anisidide, suggesting a chemical alteration of the DNA strand. Interestingly, the ability to stimulate irreversible cleavage progressively decreased over time when clerocidin was stored in ethanol. Under these conditions, nuclear magnetic resonance measurements demonstrated that the drug underwent structural modifications that involved the C-12-C-15 side chain. Thus, the results indicate that a specific moiety of clerocidin may react with the DNA (guanine at -1) in the ternary complex, resulting in cleavage irreversibility and in altered DNA mobility in sequencing gels. PMID:9135013

  7. Role of early cleavage in predicting success of intra cytoplasmic sperm injection in assisted reproductive technologies

    Directory of Open Access Journals (Sweden)

    Manjula Gopalakrishnan, Sanjeeva Reddy Nellapalli, Muthiah sinvaniah surulimuthu

    2014-07-01

    Full Text Available Aim and Objective: The present study is aimed to carry out the impact of early cleavage over late cleavage in assessing the pregnancy outcome using of Intra Cytoplasmic Sperm Injection (ICSI in assisted reproductive technologies. Materials and Methods A total of 154 patients enrolled for Intra Cytoplasmic Sperm Injection (ICSI fulfilling the selection criteria were recruited for the study at a tertiary care assisted reproductive centre. ICSI was performed 3–5 h after oocyte aspiration with the prepared sperm. All embryos were checked for early cleavage at 27 hours post intra cytoplasmic sperm injection. They were divided into two groups. Group I- Embryos which cleaved before 27 hours after Intra Cytoplasmic Sperm Injection (ICSI. Group II- Embryos which cleaved after 27 hours. The pregnancy rates were compared between the two groups. Results: All the 154 patients were analysed. There was no difference in the mean age, duration of ovarian stimulation, number of oocytes retrieved, fertilization, cleavage rates and embryo quality between the two groups. Early cleavage was observed in 98 patients (63.64 %. Late cleavage was observed in 56 patients (36.36%. The clinical pregnancy was confirmed in 59 patients (60.20% in Group I and 20 patients (35.71% in Group II which was statistically significant P <0.001. Conclusion: Early cleavage is a strong predictor of embryo quality and can predict ICSI outcome.

  8. Cleavage Site Localization Differentially Controls Interleukin-6 Receptor Proteolysis by ADAM10 and ADAM17.

    Science.gov (United States)

    Riethmueller, Steffen; Ehlers, Johanna C; Lokau, Juliane; Düsterhöft, Stefan; Knittler, Katharina; Dombrowsky, Gregor; Grötzinger, Joachim; Rabe, Björn; Rose-John, Stefan; Garbers, Christoph

    2016-01-01

    Limited proteolysis of the Interleukin-6 Receptor (IL-6R) leads to the release of the IL-6R ectodomain. Binding of the cytokine IL-6 to the soluble IL-6R (sIL-6R) results in an agonistic IL-6/sIL-6R complex, which activates cells via gp130 irrespective of whether the cells express the IL-6R itself. This signaling pathway has been termed trans-signaling and is thought to mainly account for the pro-inflammatory properties of IL-6. A Disintegrin And Metalloprotease 10 (ADAM10) and ADAM17 are the major proteases that cleave the IL-6R. We have previously shown that deletion of a ten amino acid long stretch within the stalk region including the cleavage site prevents ADAM17-mediated cleavage, whereas the receptor retained its full biological activity. In the present study, we show that deletion of a triple serine (3S) motif (Ser-359 to Ser-361) adjacent to the cleavage site is sufficient to prevent IL-6R cleavage by ADAM17, but not ADAM10. We find that the impaired shedding is caused by the reduced distance between the cleavage site and the plasma membrane. Positioning of the cleavage site in greater distance towards the plasma membrane abrogates ADAM17-mediated shedding and reveals a novel cleavage site of ADAM10. Our findings underline functional differences in IL-6R proteolysis by ADAM10 and ADAM17. PMID:27151651

  9. Sox11 Reduces Caspase-6 Cleavage and Activity.

    Directory of Open Access Journals (Sweden)

    Elaine Waldron-Roby

    Full Text Available The apoptotic cascade is an orchestrated event, whose final stages are mediated by effector caspases. Regulatory binding proteins have been identified for caspases such as caspase-3, -7, -8, and -9. Many of these proteins belong to the inhibitor of apoptosis (IAP family. By contrast, caspase-6 is not believed to be influenced by IAPs, and little is known about its regulation. We therefore performed a yeast-two-hybrid screen using a constitutively inactive form of caspase-6 for bait in order to identify novel regulators of caspase-6 activity. Sox11 was identified as a potential caspase-6 interacting protein. Sox11 was capable of dramatically reducing caspase-6 activity, as well as preventing caspase-6 self- cleavage. Several regions, including amino acids 117-214 and 362-395 within sox11 as well as a nuclear localization signal (NLS all contributed to the reduction in caspase-6 activity. Furthermore, sox11 was also capable of decreasing other effector caspase activity but not initiator caspases -8 and -9. The ability of sox11 to reduce effector caspase activity was also reflected in its capacity to reduce cell death following toxic insult. Interestingly, other sox proteins also had the ability to reduce caspase-6 activity but to a lesser extent than sox11.

  10. Calpain-mediated cleavage of DARPP-32 in Alzheimer's disease.

    Science.gov (United States)

    Cho, Kwangmin; Cho, Mi-Hyang; Seo, Jung-Han; Peak, Jongjin; Kong, Kyoung-Hye; Yoon, Seung-Yong; Kim, Dong-Hou

    2015-10-01

    Toxicity induced by aberrant protein aggregates in Alzheimer's disease (AD) causes synaptic disconnection and concomitant progressive neurodegeneration that eventually impair cognitive function. cAMP-response element-binding protein (CREB) is a transcription factor involved in the molecular switch that converts short-term to long-term memory. Although disturbances in CREB function have been suggested to cause memory deficits in both AD and AD animal models, the mechanism of CREB dysfunction is still unclear. Here, we show that the dopamine- and cAMP-regulated phosphoprotein 32 kDa (DARPP-32), a key inhibitor of protein phosphate-1 (PP-1) that regulates CREB phosphorylation, is cleaved by activated calpain in both AD brains and neuronal cells treated with amyloid-β or okadaic acid, a protein phosphatase-2A inhibitor that induces tau hyperphosphorylation and neuronal death. We found that DARPP-32 is mainly cleaved at Thr(153) by calpain and that this cleavage of DARPP-32 reduces CREB phosphorylation via loss of its inhibitory function on PP1. Our results suggest a novel mechanism of DARPP-32-CREB signalling dysregulation in AD. PMID:26178297

  11. Large volume loss during cleavage formation, Hamburg sequence, Pennsylvania

    Science.gov (United States)

    Beutner, Edward C.; Charles, Emmanuel G.

    1985-11-01

    Green reduction spots in red slate of the Hamburg sequence exposed near Shartlesville, Pennsylvania, have axial ratios of 1.42:1.0:0.28 on the limbs of near-isoclinal folds and 1.0:0.79:0.41 in fold hinge zones. Conodont cusps and denticles within the reduction spots have been brittlely pulled apart and give independent measures of extension in various directions. Comparison of conodont extensions with reduction spot shapes on limbs and hinges indicates that sedimentary compaction of 44% preceded the tectonic strain associated with cleavage formation. This strain, having identical maximum extensions but greater shortening in fold hinges as compared to limbs, was characterized by 41% extension in X, no change in Y, 50% to 59% shortening in Z, and 29% to 42% tectonic volume loss. The general lack of directed overgrowths on grains reflects the large volume loss and contrasts with other slates, where deformation was an almost constant volume process and extension in X compensated for shortening in Z. *Present address: Department of Geology, Miami University, Oxford, Ohio 45056

  12. Transcriptome-Wide Cleavage Site Mapping on Cellular mRNAs Reveals Features Underlying Sequence-Specific Cleavage by the Viral Ribonuclease SOX.

    Directory of Open Access Journals (Sweden)

    Marta Maria Gaglia

    2015-12-01

    Full Text Available Many viruses express factors that reduce host gene expression through widespread degradation of cellular mRNA. An example of this class of proteins is the mRNA-targeting endoribonuclease SOX from the gamma-herpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV. Previous studies indicated that cleavage of messenger RNAs (mRNA by SOX occurs at specific locations defined by the sequence of the target RNA, which is at odds with the down-regulation of a large portion of cellular transcripts. In this study, we address this paradox by using high-throughput sequencing of cleavage intermediates combined with a custom bioinformatics-based analysis pipeline to identify SOX cleavage sites across the mRNA transcriptome. These data, coupled with targeted mutagenesis, reveal that while cleavage sites are specific and reproducible, they are defined by a degenerate sequence motif containing a small number of conserved residues rather than a strong consensus sequence. This degenerate element is well represented in both human and KSHV mRNA, and its presence correlates with RNA destabilization by SOX. This represents a new endonuclease targeting strategy, in which use of a degenerate targeting element enables RNA cleavage at specific locations without restricting the range of targets. Furthermore, it shows that strong target selectivity can be achieved without a high degree of sequence specificity.

  13. Characterization of the (0001) cleavage surface of antimony single crystals using scanning probe microscopy: Atomic structure, vacancies, cleavage steps, and twinned interlayers

    Science.gov (United States)

    Stegemann, Bert; Ritter, Claudia; Kaiser, Bernhard; Rademann, Klaus

    2004-04-01

    Atomically resolved scanning tunneling microscopy images of the unreconstructed hexagonal structure of surface atoms on Sb(0001) are presented. Lateral and vertical lattice parameters have been determined. The interatomic spacing of 4.31 Å (±0.05 Å) on the Sb(0001) surface corresponds to the known bulk data. Cleavage has been found to occur always between adjacent double layers, yielding at least diatomic cleavage steps of 3.75 Å (±0.10 Å) height. Different kinds of defect structures on the cleavage plane have been imaged with atomic resolution. Point defects, caused by a single or by three missing surface atoms, have been uncovered. Stable imaging of cleavage steps, which were found to be straight along the atomic rows, has been achieved. Twinned interlayers formed upon cleavage of Sb even at room temperature have been revealed by atomic force microscopy. The mean twinning angle of 2.42° (±0.20°) is quantitatively in accord with the value of 2.45° predicted by the model of twinning in Sb crystals. The observed features are discussed with respect to other layered materials and with regard to their relevance for the use of Sb(0001) as a support of nanostructures.

  14. Intracellular ribozyme-catalyzed trans-cleavage of RNA monitored by fluorescence resonance energy transfer.

    Science.gov (United States)

    Vitiello, D; Pecchia, D B; Burke, J M

    2000-04-01

    Small catalytic RNAs like the hairpin ribozyme are proving to be useful intracellular tools; however, most attempts to demonstrate trans-cleavage of RNA by ribozymes in cells have been frustrated by rapid cellular degradation of the cleavage products. Here, we describe a fluorescence resonance energy transfer (FRET) assay that directly monitors cleavage of target RNA in tissue-culture cells. An oligoribonucleotide substrate was modified to inhibit cellular ribonuclease degradation without interfering with ribozyme cleavage, and donor (fluorescein) and acceptor (tetramethylrhodamine) fluorophores were introduced at positions flanking the cleavage site. In simple buffers, the intact substrate produces a strong FRET signal that is lost upon cleavage, resulting in a red-to-green shift in dominant fluorescence emission. Hairpin ribozyme and fluorescent substrate were microinjected into murine fibroblasts under conditions in which substrate cleavage can occur only inside the cell. A strong FRET signal was observed by fluorescence microscopy when substrate was injected, but rapid decay of the FRET signal occurred when an active, cognate ribozyme was introduced with the substrate. No acceleration in cleavage rates was observed in control experiments utilizing a noncleavable substrate, inactive ribozyme, or an active ribozyme with altered substrate specificity. Subsequently, the fluorescent substrates were injected into clonal cell lines that expressed cognate or noncognate ribozymes. A decrease in FRET signal was observed only when substrate was microinjected into cells expressing its cognate ribozyme. These results demonstrate trans-cleavage of RNA within mammalian cells, and provide an experimental basis for quantitative analysis of ribozyme activity and specificity within the cell. PMID:10786853

  15. Interpreting Dual Laterolog Fracture Data in Fractured Carbonate Formation

    Institute of Scientific and Technical Information of China (English)

    Deng Shaogui; Wang Xiaochang; Zou Dejiang; Fan Yiren; Yang Zhen

    2006-01-01

    The estimation of fractures is key to evaluating fractured carbonate reservoirs. It is difficult to evaluate this kind of reservoir because of its heterogeneously distributed fractures and anisotropy.A three-dimensional numerical model was used to simulate the responses of the dual laterolog (DLL) in a fractured formation based on a macro-isotropic anisotropic model. Accordingly, a fast fracturecomputing method was developed. First, the apparent conductivity of the DLL is linearly related to the porosity of the fracture and the conductivity of pore fluid. Second, the amplitude difference of the deep and shallow apparent resistivity logs is mainly dependenton the dip angle of the fracture. Then the response of the DLL to a formation with dip angle fracturesis approximately depicted as a function of the bulk resistivity of the rock, the porosity of the fractures and the conductivity of fracture fluid. This function can be used to compute the porosity of fracture quickly. The actual data show that the fracture parameters determined by the DLL closely coincide with the formation micro imager log.

  16. Elastic-plastic fracture mechanics of strength-mismatching

    Energy Technology Data Exchange (ETDEWEB)

    Parks, D.M.; Ganti, S.; McClintock, F.A. [Massachusetts Institute of Technology, Cambridge, MA (United States)

    1996-12-31

    Approximate solutions to stress-fields are provided for a strength-mismatched interface crack in small-scale yielding (SSY) for non-hardening and low hardening materials. Variations of local deformation intensities, characterized by a J-type contour integral, are proposed. The softer material experiences a higher deformation intensity level, J{sub S}, while the harder material sees a much lower deformation intensity level, J{sub H}, compared to that obtained from the applied J near the respective homogeneous crack-tips. For a low hardening material, the stress fields are obtained by scaling from an elastic/perfectly-plastic problem, based on an effective mismatch, M{sub eff}, which is a function of mismatch, M, and the hardening exponent, n. Triaxial stress build-up is discussed quantitatively in terms of M. The influence of strength-mismatch on cleavage fracture is discussed using Weibull statistics.

  17. Constraint effects on fracture toughness of impact-loaded, precracked Charpy specimens

    International Nuclear Information System (INIS)

    Impact-loaded, precracked Charpy specimens often play a crucial role in irradiation surveillance programs for nuclear power plants. However, the small specimen size B=W=10 mm limits the maximum value of cleavage fracture toughness Jc that can be measured under elastic-plastic conditions without loss of crack tip constraint. In this investigation, plane strain impact analyses provide detailed resolution of crack tip fields for impact-loaded specimens. Crack tip stress fields are characterized in terms of J-Q trajectories and the toughness-scaling model which is applicable for a cleavage fracture mechanism. Results of the analyses suggest deformation limits at fracture in the form of b>MJc/σ0, where M approaches 25-30 for a strongly rate-sensitive material at impact velocities of 3-6 m s-1. Based on direct comparison of the static and dynamic J values computed using a domain integral formulation, a new proposal emerges for the transition time, the time after impact at which interial effects diminish sufficiently for simple evaluation of J using the plastic η factor approach. (orig.)

  18. The short transcript of Leishmania RNA virus is generated by RNA cleavage.

    OpenAIRE

    MacBeth, K J; Patterson, J. L.

    1995-01-01

    Leishmania RNA virus 1 produces a short viral RNA transcript corresponding to the 5' end of positive-sense single-stranded RNAs both in virally infected cells and in in vitro polymerase assays. We hypothesized that this short transcript was generated via cleavage of full-length positive-sense single-stranded RNA. A putative cleavage site was mapped by primer extension analysis to nucleotide 320 of the viral genome. To address the hypothesis that the short transcript is generated via cleavage ...

  19. Methylase-limited partial NotI cleavage for physical mapping of genomic DNA.

    OpenAIRE

    Hanish, J; McClelland, M

    1990-01-01

    Partial cleavage of DNA with the restriction endonuclease NotI (5'...GC/GGCCGC...3') is an important technique for genomic mapping. However, partial genomic cleavage with this enzyme is impaired by the agarose matrix in which the DNA must be suspended. To solve this problem we have purified the blocking methylase M. BspRI (5'...GGmCC...3') for competition digests with NotI. The resulting methylase-limited partial DNA cleavage is shown to be superior to standard techniques on bacterial genomic...

  20. Enhanced cleavage of type II collagen by collagenases in osteoarthritic articular cartilage.

    OpenAIRE

    Billinghurst, R.C.; Dahlberg, L; Ionescu, M.; Reiner, A; Bourne, R; Rorabeck, C; Mitchell, P; Hambor, J; Diekmann, O.; Tschesche, H; Chen, J; Van Wart, H; Poole, A. R.

    1997-01-01

    We demonstrate the direct involvement of increased collagenase activity in the cleavage of type II collagen in osteoarthritic human femoral condylar cartilage by developing and using antibodies reactive to carboxy-terminal (COL2-3/4C(short)) and amino-terminal (COL2-1/4N1) neoepitopes generated by cleavage of native human type II collagen by collagenase matrix metalloproteinase (MMP)-1 (collagenase-1), MMP-8 (collagenase-2), and MMP-13 (collagenase-3). A secondary cleavage followed the initia...

  1. Processing of pestivirus polyprotein: cleavage site between autoprotease and nucleocapsid protein of classical swine fever virus.

    OpenAIRE

    Stark, R; Meyers, G; Rümenapf, T.; Thiel, H J

    1993-01-01

    The polyprotein of classical swine fever virus starts with the nonstructural protein p23, which is followed by the nucleocapsid protein p14. Proteolytic cleavage between p23 and p14 was demonstrated in a cell-free transcription-translation system. Successive truncation of the cDNA used for the transcription indicated that the proteolytic activity responsible for the cleavage between p23 and p14 resides within p23. In order to determine the cleavage site between these two proteins, the respect...

  2. Preferential DNA Cleavage under Anaerobic Conditions by a DNA Binding Ruthenium Dimer

    OpenAIRE

    Janaratne, Thamara K.; Ongeri, Fiona; Yadav, Abishek; MacDonnell, Frederick M.

    2007-01-01

    In the absence of O2, the cationic complex, [(phen)2Ru(tatpp)Ru(phen)2]4+ (P4+), undergoes in situ reduction by glutathione (GSH) to form a species that induces DNA cleavage. Exposure to air strongly attenuates the cleavage activity, even in the presence of a large excess of reducing agent (e.g., 40 equiv GSH per P4+) suggesting the complex may be useful in targeting cells with a low oxygen microenvironment (hypoxia) for destruction via DNA cleavage. The active species is identified as the do...

  3. Mechanisms of RNAi: mRNA cleavage fragments may indicate stalled RISC

    OpenAIRE

    Holen, Torgeir

    2005-01-01

    The molecular mechanism of RNA interference (RNAi) is under intense investigation. We previously demonstrated the existence of inactive siRNAs and also of mRNA cleavage in vivo in human cells. Here it is shown that some siRNAs with low activity leave mRNA cleavage fragments while an siRNA with higher activity does not. The pattern is consistent with both short-term (4-24 hours) and long-term (1-4 days) time-series. Analysis of the putative 3′ mRNA cleavage product showed high GC content immed...

  4. Guest-host interactions in the cleavage of phenylphenyl acetates by -cyclodextrin in alkaline medium

    Indian Academy of Sciences (India)

    V Raj; T Chandrakala; K Rajasekaran

    2008-05-01

    Kinetics of cleavage of phenylphenyl acetates (PPA) and several para-substituted PPAs in basic aqueous sodium carbonate-bicarbonate buffer containing -cyclodextrin (CD) have been studied. The reaction exhibits saturation type kinetics and CD accelerates the rate of cleavage by the formation of 1G : 1H inclusion complex. The kinetic results indicate that aryloxy moiety of PPA is included in the hydrophobic cavity of CD. The overall rate constants for the cleavage of the [CD-ester] complex correlate with the Hammett -constants and Hansch hydrophobicity parameters . At higher concentrations of CD, there is an additional catalysis due to the formation of weak 1G : 2H complex.

  5. Coexistence of ductile and brittle fracture in metals

    International Nuclear Information System (INIS)

    It is well known that semibrittle body-centered cubic (bcc) metals fail at low temperatures by cleavage that is preceded by crack tip deformation. Sinclair and Finnis proposed a mechanism by which crack tip deformation may be combined with brittle crack extension. In this model, edge dislocations are emitted from a crack tip on an inclined plane under pure mode I loading conditions. The authors propose a new mechanism of brittle fracture of semibrittle metals preceded by crack tip deformation by extending the model of Sinclair and Finnis and by incorporating experimental evidence on mixed mode crack propagation observed by transmission electron microscopy (TEM). They have shown experimentally that, even when the orientation of the dislocations in the plastic zone indicated pure mode III crack tip deformation, the crack opening displacement determined from the relative displacement of the crack flanks showed the presence of an additional mode I component. They have also shown that zigzag crack propagation observed in many metals can occur only if mode I cleavage is superimposed to mode II crack tip deformation

  6. Vertebral fracture classification

    Science.gov (United States)

    de Bruijne, Marleen; Pettersen, Paola C.; Tankó, László B.; Nielsen, Mads

    2007-03-01

    A novel method for classification and quantification of vertebral fractures from X-ray images is presented. Using pairwise conditional shape models trained on a set of healthy spines, the most likely unfractured shape is estimated for each of the vertebrae in the image. The difference between the true shape and the reconstructed normal shape is an indicator for the shape abnormality. A statistical classification scheme with the two shapes as features is applied to detect, classify, and grade various types of deformities. In contrast with the current (semi-)quantitative grading strategies this method takes the full shape into account, it uses a patient-specific reference by combining population-based information on biological variation in vertebra shape and vertebra interrelations, and it provides a continuous measure of deformity. Good agreement with manual classification and grading is demonstrated on 204 lateral spine radiographs with in total 89 fractures.

  7. Fracture of brittle solids

    CERN Document Server

    Lawn, Brian

    1993-01-01

    This is an advanced text for higher degree materials science students and researchers concerned with the strength of highly brittle covalent-ionic solids, principally ceramics. It is a reconstructed and greatly expanded edition of a book first published in 1975. The book presents a unified continuum, microstructural and atomistic treatment of modern day fracture mechanics from a materials perspective. Particular attention is directed to the basic elements of bonding and microstructure that govern the intrinsic toughness of ceramics. These elements hold the key to the future of ceramics as high-technology materials--to make brittle solids strong, we must first understand what makes them weak. The underlying theme of the book is the fundamental Griffith energy-balance concept of crack propagation. The early chapters develop fracture mechanics from the traditional continuum perspective, with attention to linear and nonlinear crack-tip fields, equilibrium and non-equilibrium crack states. It then describes the at...

  8. Dictionary of fracture mechanics

    International Nuclear Information System (INIS)

    7000 entries summarize the most important and frequently used terms in fracture mechanics: modes of fracture, concepts and criteria, cracks and crack growth, test methods, specimens etc. Some general terms that have a special meaning in the scope of this book are also included as are important abbreviations, acronyms, symbols and units. All entries are alphabetically ordered and, if appropriate, combined with groups of related words. Groups of word combinations are thought to be useful for the understanding of linguistic laws. Annotations in italics may be helpful in relating the entry to a special technical scope. Within the entries the source-language terms are bold-faced. In the German alphabet the mutated vowels ae, oe and ue are ordered as ae, oe and ue; ss is ordered as ss. (orig./HP)

  9. Melt fracture revisited

    Energy Technology Data Exchange (ETDEWEB)

    Greenberg, J. M.

    2003-07-16

    In a previous paper the author and Demay advanced a model to explain the melt fracture instability observed when molten linear polymer melts are extruded in a capillary rheometer operating under the controlled condition that the inlet flow rate was held constant. The model postulated that the melts were a slightly compressible viscous fluid and allowed for slipping of the melt at the wall. The novel feature of that model was the use of an empirical switch law which governed the amount of wall slip. The model successfully accounted for the oscillatory behavior of the exit flow rate, typically referred to as the melt fracture instability, but did not simultaneously yield the fine scale spatial oscillations in the melt typically referred to as shark skin. In this note a new model is advanced which simultaneously explains the melt fracture instability and shark skin phenomena. The model postulates that the polymer is a slightly compressible linearly viscous fluid but assumes no slip boundary conditions at the capillary wall. In simple shear the shear stress {tau}and strain rate d are assumed to be related by d = F{tau} where F ranges between F{sub 2} and F{sub 1} > F{sub 2}. A strain rate dependent yield function is introduced and this function governs whether F evolves towards F{sub 2} or F{sub 1}. This model accounts for the empirical observation that at high shears polymers align and slide more easily than at low shears and explains both the melt fracture and shark skin phenomena.

  10. Phase Field Fracture Mechanics.

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Brett Anthony [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-11-01

    For this assignment, a newer technique of fracture mechanics using a phase field approach, will be examined and compared with experimental data for a bend test and a tension test. The software being used is Sierra Solid Mechanics, an implicit/explicit finite element code developed at Sandia National Labs in Albuquerque, New Mexico. The bend test experimental data was also obtained at Sandia Labs while the tension test data was found in a report online from Purdue University.

  11. Atypical femoral fractures

    OpenAIRE

    Giannini, Sandro; Chiarello, Eugenio; Tedesco, Giuseppe; Cadossi, Matteo; Luciani, Deianira; Mazzotti, Antonio; Donati, Davide Maria

    2013-01-01

    Bisphosphonates (BPs) represent the most widely used therapy for osteoporosis. Recently, a relationship between long-term treatment with BPs and a subset of atypical femoral fractures (AFFs) from below the lesser trochanter to the sovracondilar line has been described. Many etiopathogenetic theories have been invoked to explain AFFs: reduced bone turnover and increased osteoblast bone apposition with accumulation of microdamage and decreased bone toughness with subsequent increased risk of mi...

  12. Technical report on micro-mechanical versus conventional modelling in non-linear fracture mechanics

    International Nuclear Information System (INIS)

    While conventional fracture mechanics is capable of predicting crack growth behaviour if sufficient experimental observations are available, micro-mechanical modelling can both increase the accuracy of these predictions and model phenomena that are inaccessible by the conventional theory such as the ductile-cleavage temperature transition. A common argument against micro-mechanical modelling is that it is too complicated for use in routine engineering applications. This is both a computational and an educational problem. That micro-mechanical modelling is unnecessarily complicated is certainly true in many situations. The on-going development of micro-mechanical models, computational algorithms and computer speed will however most probably diminish the computational problem rather rapidly. Compare for instance the rate of development of computational methods for structural analysis. Meanwhile micro-mechanical modelling may serve as a tool by which more simplified engineering methods can be validated. The process of receiving a wide acceptance of the new methods is probably much slower. This involves many steps. First the research community must be in reasonable agreement on the methods and their use. Then the methods have to be implemented into computer software and into code procedures. The development and acceptance of conventional fracture mechanics may serve as an historical example of the time required before a new methodology has received a wide usage. The CSNI Working Group on Integrity and Ageing (IAGE) decided to carry out a report on micro-mechanical modeling to promote this promising and valuable technique. The report presents a comparison with non-linear fracture mechanics and highlights key aspects that could lead to a better knowledge and accurate predictions. Content: - 1. Introduction; - 2. Concepts of non-linear fracture mechanics with point crack tip modelling; - 3. Micro-mechanical models for cleavage fracture; - 4, Micro-mechanical modelling of

  13. Double segmental tibial fractures - an unusual fracture pattern

    Directory of Open Access Journals (Sweden)

    Bali Kamal

    2012-02-01

    Full Text Available 【Abstract】A case of a 50-year-old pedestrian who was hit by a bike and suffered fractures of both bones of his right leg was presented. Complete clinical and radiographic assessment showed double segmental fractures of the tibia and multisegmental fractures of the fibula. Review of the literature revealed that this fracture pattern was unique and only a single case was reported so far. Moreover, we discussed the possible mechanisms which can lead to such an injury. We also discussed the management of segmental tibial fracture and the difficulties encountered with them. This case was managed by modern osteosynthesis tech- nique with a pleasing outcome. Key words: Fracture, bone; Tibia; Fibula; Nails

  14. Zoledronic acid and clinical fractures and mortality after hip fracture

    DEFF Research Database (Denmark)

    Lyles, Kenneth W; Colón-Emeric, Cathleen S; Magaziner, Jay S;

    2007-01-01

    BACKGROUND: Mortality is increased after a hip fracture, and strategies that improve outcomes are needed. METHODS: In this randomized, double-blind, placebo-controlled trial, 1065 patients were assigned to receive yearly intravenous zoledronic acid (at a dose of 5 mg), and 1062 patients were...... assigned to receive placebo. The infusions were first administered within 90 days after surgical repair of a hip fracture. All patients (mean age, 74.5 years) received supplemental vitamin D and calcium. The median follow-up was 1.9 years. The primary end point was a new clinical fracture. RESULTS: The...... rates of any new clinical fracture were 8.6% in the zoledronic acid group and 13.9% in the placebo group, a 35% risk reduction with zoledronic acid (P=0.001); the respective rates of a new clinical vertebral fracture were 1.7% and 3.8% (P=0.02), and the respective rates of new nonvertebral fractures...

  15. Potential impact of enhanced fracture-toughness data on pressurized-thermal-shock analysis

    International Nuclear Information System (INIS)

    The Heavy Section Steel Technology (HSST) Program is involved with the generation of ''enhanced'' fracture-initiation toughness and fracture-arrest toughness data of prototypic nuclear reactor vessel steels. These two sets of data are enhanced because they have distinguishing characteristics that could potentially impact PWR pressure vessel integrity assessments for the pressurized-thermal shock (PTS) loading condition which is a major plant-life extension issue to be confronted in the 1990's. Currently, the HSST Program is planning experiments to verify and quantify, for A533B steel, the distinguishing characteristic of elevated initiation-fracture toughness for shallow flaws which has been observed for other steels. Deterministic and probabilistic fracture-mechanics analyses were performed to examine the influence of the enhanced initiation and arrest fracture-toughness data on the cleavage fracture response of a nuclear reactor pressure vessel subjected to PTS loading. The results of the analyses indicated that application of the enhanced KIa data does reduce the conditional probability of failure P(F|E); however, it does not appear to have the potential to significantly impact the results of PTS analyses. The application of enhanced fracture-initiation-toughness data for shallow flaws also reduces P(F|E), but it does appear to have a potential for significantly affecting the results of PTS analyses. The effect of including Type I warm prestress in probabilistic fracture-mechanics analyses is beneficial. The benefit is transient dependent and, in some cases, can be quite significant. 19 refs., 12 figs., 1 tab

  16. Fracture behavior of Alloy 625 with different precipitate microstructures

    International Nuclear Information System (INIS)

    To study the effect of various ordered phases and their growth on room temperature tensile properties and fracture behavior of Alloy 625, specimens of this alloy were held isothermally at 813 K, 973 K and 1123 K for 10 h, 100 h and 1200 h, respectively. Specimens held at the aforementioned temperatures were subjected to transmission electron microscopic investigation to characterize Ni2(Cr,Mo), γ″ and δ ordered phases. Tensile testing of the heat-treated samples revealed the influence of these ordered phases on the tensile properties and fractures. Primary carbides, which were identified semi-qualitatively under electron-probe micro-analyzer (EPMA) have been found responsible for void nucleation resulting in large dimples in Alloy 625 with solid-solution matrix. Early stages of Ni2(Cr,Mo) and γ″ and their subsequent growth at 813 K, was responsible for increase in strength without reducing ductility considerably. This behavior has been correlated with the reduction in size and depth of the dimples in the fractographs. Transmission electron micrographs showing three variants of γ″ in three orthogonal directions in the alloy matrix have revealed that the morphology of the ordered phase is lens shaped and the precipitate can grow up to ∼150 nm. With the growth of γ″ the alloy is seen to fracture in transgranular cleavage manner following ∼23% of uniform strain. Influence of plate shaped, long and thick δ phase on the strength and ductility appears similar to that of γ″. δ—precipitation after 1200 h of isothermal holding at 1123 K is also seen to cause faceted appearance of the fracture surface, which is similar to that of γ″ after 1200 h of isothermal holding at 973 K. However, the facets are seen to be consisting of dimples, which are small and uniformly distributed over the surface

  17. Kinetics and regulation of site-specific endonucleolytic cleavage of human IGF-II mRNAs

    OpenAIRE

    van Dijk, Erwin L.; Sussenbach, John S.; Holthuizen, P. Elly

    2001-01-01

    Human insulin-like growth factor II (IGF-II) mRNA can be cleaved at a specific site in its 4 kb long 3′-UTR. This yields a stable 3′ cleavage product of 1.8 kb consisting of a 3′-UTR and a poly(A) tail and an unstable 5′ cleavage product containing the IGF-II coding region. After cleavage, the 5′ cleavage product is targeted to rapid degradation and consequently is no longer involved in IGF-II protein synthesis. Cleavage is therefore thought to provide an addit...

  18. The intramembrane cleavage site of the amyloid precursor protein depends on the length of its transmembrane domain

    OpenAIRE

    Lichtenthaler, Stefan F.; Beher, Dirk; Heike S Grimm; Wang, Rong; Shearman, Mark S.; Masters, Colin L.; Beyreuther, Konrad

    2002-01-01

    Proteolytic processing of the amyloid precursor protein by β-secretase generates C99, which subsequently is cleaved by γ-secretase, yielding the amyloid β peptide (Aβ). This γ-cleavage occurs within the transmembrane domain (TMD) of C99 and is similar to the intramembrane cleavage of Notch. However, Notch and C99 differ in their site of intramembrane cleavage. The main γ-cleavage of C99 occurs in the middle of the TMD, whereas the cleavage of Notch occurs close to the C-terminal end of the TM...

  19. An investigation into the role of ATP in the mammalian pre-mRNA 3' cleavage reaction.

    Science.gov (United States)

    Khleborodova, Asya; Pan, Xiaozhou; Nagre, Nagaraja N; Ryan, Kevin

    2016-06-01

    RNA Polymerase II transcribes beyond what later becomes the 3' end of a mature messenger RNA (mRNA). The formation of most mRNA 3' ends results from pre-mRNA cleavage followed by polyadenylation. In vitro studies have shown that low concentrations of ATP stimulate the 3' cleavage reaction while high concentrations inhibit it, but the origin of these ATP effects is unknown. ATP might enable a cleavage factor kinase or activate a cleavage factor directly. To distinguish between these possibilities, we tested several ATP structural analogs in a pre-mRNA 3' cleavage reaction reconstituted from DEAE-fractionated cleavage factors. We found that adenosine 5'-(β,γ-methylene)triphosphate (AMP-PCP) is an effective in vitro 3' cleavage inhibitor with an IC50 of ∼300 μM, but that most other ATP analogs, including adenosine 5'-(β,γ-imido)triphosphate, which cannot serve as a protein kinase substrate, promoted 3' cleavage but less efficiently than ATP. In combination with previous literature data, our results do not support ATP stimulation of 3' cleavage through cleavage factor phosphorylation in vitro. Instead, the more likely mechanism is that ATP stimulates cleavage factor activity through direct cleavage factor binding. The mammalian 3' cleavage factors known to bind ATP include the cleavage factor II (CF IIm) Clp1 subunit, the CF Im25 subunit and poly(A) polymerase alpha (PAP). The yeast homolog of the CF IIm complex also binds ATP through yClp1. To investigate the mammalian complex, we used a cell-line expressing FLAG-tagged Clp1 to co-immunoprecipitate Pcf11 as a function of ATP concentration. FLAG-Clp1 co-precipitated Pcf11 with or without ATP and the complex was not affected by AMP-PCP. Diadenosine tetraphosphate (Ap4A), an ATP analog that binds the Nudix domain of the CF Im25 subunit with higher affinity than ATP, neither stimulated 3' cleavage in place of ATP nor antagonized ATP-stimulated 3' cleavage. The ATP-binding site of PAP was disrupted by site

  20. Human pre-mRNA cleavage factor II(m) contains homologs of yeast proteins and bridges two other cleavage factors

    OpenAIRE

    de Vries, H.; Rüegsegger, U.; Hübner, W; Friedlein, A.; van Langen, H; Keller, W.

    2000-01-01

    Six different protein factors are required in vitro for 3' end formation of mammalian pre-mRNAs by endonucleolytic cleavage and polyadenylation. Five of the factors have been purified and most of their components cloned, but cleavage factor II(m) (CF II(m)) remained uncharacterized. We have purified CF II(m) from HeLa cell nuclear extract by several chromatographic steps. During purification, CF II(m) activity separated into two components, one essential (CF IIA(m)) and one stimulatory (CF II...

  1. Limit of the local approach application of the brittle fracture on hydrogen charged steels

    International Nuclear Information System (INIS)

    The local approach of the brittle fracture by cleavage developed by BEREMIN relies the macroscopic mechanical properties to local criteria. It allows to predict the probability of failure of the structure by performing detailed calculation of the stress and deformation fields in the different element volumes within this structure. It also takes into account the distribution of the defects initiating the fracture in a specific zone. The local approach allows then the determination of a statistical criterion to be applied on cleavage fracture. The cumulative distribution function PR, over a small volume V0 ahead of a crack tip or defect can be expressed as: PR 1 - exp[-σw/σu)m] where σw WEIBULL stress and σu mean cleavage stress defined as the stress / volume leading to PR = 0.63 and m is an empirically determined parameter presenting the degree of scatter in measured strength values. The paper deals with the application of this approach on three steels in absence and in presence of hydrogen: railway steel FM80, with pearlitic structure, 35CD4 steel employed in tool's joints in a tempered martensitic state and a bainitic A508.3 used in nuclear power plants. The goal of this work is to show that in the case hydrogenated steel, the local approach is improved if the defects promoted by high stress triaxiality and local critical hydrogen concentration do not exceed the element volume V0 in which the material is considered to be statistically homogeneous. The results show that in the two first steel the local approach is improved even in presence of hydrogen. In the hydrogenated bainitic steel (A508.3), the application of this method is not possible due to development in the material of fish eyes which the size is very large with respect to V0. (author). 7 refs., 4 figs., 1 tab

  2. Mortality after hip fracture with vertebral compression fracture is poor.

    Science.gov (United States)

    Imai, Norio; Endo, Naoto; Hoshino, Tadashi; Suda, Ken; Miyasaka, Dai; Ito, Tomoyuki

    2016-01-01

    Due to the increasing elderly population, the prevalence of osteoporotic hip fractures in Japanese patients continues to rise. It is well established that patients with either hip fracture or both symptomatic and asymptomatic morphometric vertebral compression fracture (VCF) have a poor health prognosis compared with the general population. The purpose of this study was to retrospectively investigate vertebral fracture rates among patients with hip fracture and their influence on mortality. We examined 182 cases of osteoporotic hip fracture in patients admitted to our institution between January 2009 and May 2011. The average age at the time of fracture was 85 years. Radiographs of the lumbar spine were obtained from all of the participants and the lateral spinal radiographs were examined for evidence of VCF. The patients were classified into two groups, those with VCF and those without. A VCF was identified in approximately 78 % of the patients. The mortality rate 1 year after the hip fracture was approximately 22 % and it was significantly higher in patients with VCF. Through multivariate statistics we found that VCF, post-operative complication, loss of ambulation after operation and medication for osteoporosis were statistically significant. In other words, VCF, post-operative complication and loss of ambulation were considered to be poor prognostic factors and medication for osteoporosis was likely to improve the prognosis. We concluded that the risk of mortality after hip fracture is significantly greater in patients who also have VCF compared to patients without VCF, and that medication for osteoporosis is likely to improve prognosis. PMID:25501699

  3. Double segmental tibial fractures - an unusual fracture pattern

    OpenAIRE

    Bali Kamal; Kumar Vishal; Patel Sandeep; Aggarwal Sameer

    2012-01-01

    【Abstract】A case of a 50-year-old pedestrian who was hit by a bike and suffered fractures of both bones of his right leg was presented. Complete clinical and radiographic assessment showed double segmental fractures of the tibia and multisegmental fractures of the fibula. Review of the literature revealed that this fracture pattern was unique and only a single case was reported so far. Moreover, we discussed the possible mechanisms which can lead to such an injury. We also discussed the...

  4. Fractures in the growing foal. Part 1: Epiphyseal fractures

    International Nuclear Information System (INIS)

    This paper discusses general considerations for epiphyseal fractures and the anatomical differences which led to the Salter-Harris-classification are explained. The various locations and fracture configurations in the different bones are mentioned, and suggestions for their treatment are made. Epiphyseal fractures in growing foals have generally a favourable prognosis for healing, if treated properly. However, the prognosis for future use as an athlete has to be judged as guarded. The limb with an epiphyseal fracture should under any circumstances be splinted or cast for the transport to hospital. Epiphyseal fractures of the distal portions of the limb may be treated by cast application in some cases. More frequently, however, surgical reduction followed by some form of internal fixation is preferred. It is important to follow the basic principles of internal fixation. The implants should be removed at the earliest convenience, to prevent undue growth disturbances. Epiphyseal fractures should be treated as soon as possible to avoid further destruction of the growth plate through continuous movement at the fracture site. Growth disturbances are the most frequently encountered complications with epiphyseal fractures. Other complications include infection, osteomyelitis, degenerative joint disease and breakdown of the fracture fixation

  5. Evaluation of five fracture models in Taylor impact fracture

    Science.gov (United States)

    Zhang, Wei; Xiao, Xin-Ke; Wei, Gang; Guo, Zitao

    2012-03-01

    Taylor impact test presented in a previous study on a commercial high strength and super hard aluminum alloy 7A04-T6 are numerically evaluated using the finite element code ABAQUS/Explicit. In the present study, the influence of fracture criterion in numerical simulations of the deformation and fracture behavior of Taylor rod has been studied. Included in the paper are a modified version of Johnson-Cook, the Cockcroft-Latham(C-L), the constant fracture strain, the maximum shear stress and the maximum principle stress fracture models. Model constants for each criterion are calibrated from material tests. The modified version of Johnson-Cook fracture criterion with the stress triaxiality cut off idea is found to give good prediction of the Taylor impact fracture behavior. However, this study will also show that the C-L fracture criterion where only one simple material test is required for calibration is found to give reasonable predictions. Unfortunately, the other three criteria are not able to repeat the experimentally obtained fracture behavior. The study indicates that the stress triaxiality cut off idea is necessary to predict the Taylor impact fracture.

  6. FRACTURED PETROLEUM RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Abbas Firoozabadi

    1999-06-11

    The four chapters that are described in this report cover a variety of subjects that not only give insight into the understanding of multiphase flow in fractured porous media, but they provide also major contribution towards the understanding of flow processes with in-situ phase formation. In the following, a summary of all the chapters will be provided. Chapter I addresses issues related to water injection in water-wet fractured porous media. There are two parts in this chapter. Part I covers extensive set of measurements for water injection in water-wet fractured porous media. Both single matrix block and multiple matrix blocks tests are covered. There are two major findings from these experiments: (1) co-current imbibition can be more efficient than counter-current imbibition due to lower residual oil saturation and higher oil mobility, and (2) tight fractured porous media can be more efficient than a permeable porous media when subjected to water injection. These findings are directly related to the type of tests one can perform in the laboratory and to decide on the fate of water injection in fractured reservoirs. Part II of Chapter I presents modeling of water injection in water-wet fractured media by modifying the Buckley-Leverett Theory. A major element of the new model is the multiplication of the transfer flux by the fractured saturation with a power of 1/2. This simple model can account for both co-current and counter-current imbibition and computationally it is very efficient. It can be orders of magnitude faster than a conventional dual-porosity model. Part II also presents the results of water injection tests in very tight rocks of some 0.01 md permeability. Oil recovery from water imbibition tests from such at tight rock can be as high as 25 percent. Chapter II discusses solution gas-drive for cold production from heavy-oil reservoirs. The impetus for this work is the study of new gas phase formation from in-situ process which can be significantly

  7. Urokinase-catalysed cleavage of the urokinase receptor requires an intact glycolipid anchor

    DEFF Research Database (Denmark)

    Høyer-Hansen, G; Pessara, U; Holm, A;

    2001-01-01

    reaction, even though the actual cleavage occurs between the first and second domains. Purified full-length GPI-anchored uPAR (GPI-uPAR) proved much more susceptible to uPA-mediated cleavage than recombinant truncated soluble uPAR (suPAR), which lacks the glycolipid anchor. This was not a general...... difference in proteolytic susceptibility since GPI-uPAR and suPAR were cleaved with equal efficiency by plasmin. Since the amino acid sequences of GPI-uPAR and suPAR are identical except for the C-terminal truncation, the different cleavage patterns suggest that the two uPAR variants differ in the......PAR, purified from plasma, was found to have a similar resistance to uPA cleavage as phospholipase C-treated GPI-uPAR and recombinant suPAR....

  8. Complex Fluids and Hydraulic Fracturing.

    Science.gov (United States)

    Barbati, Alexander C; Desroches, Jean; Robisson, Agathe; McKinley, Gareth H

    2016-06-01

    Nearly 70 years old, hydraulic fracturing is a core technique for stimulating hydrocarbon production in a majority of oil and gas reservoirs. Complex fluids are implemented in nearly every step of the fracturing process, most significantly to generate and sustain fractures and transport and distribute proppant particles during and following fluid injection. An extremely wide range of complex fluids are used: naturally occurring polysaccharide and synthetic polymer solutions, aqueous physical and chemical gels, organic gels, micellar surfactant solutions, emulsions, and foams. These fluids are loaded over a wide range of concentrations with particles of varying sizes and aspect ratios and are subjected to extreme mechanical and environmental conditions. We describe the settings of hydraulic fracturing (framed by geology), fracturing mechanics and physics, and the critical role that non-Newtonian fluid dynamics and complex fluids play in the hydraulic fracturing process. PMID:27070765

  9. Social inequality and hip fracture

    DEFF Research Database (Denmark)

    Harvey, N. C.; Hansen, L.; Judge, A.;

    2015-01-01

    Social inequality appears to be increasing in many countries. We explored whether risk of hip fracture was associated with markers of inequality and whether these relationships changed with time, using data from Danish Health Registries. Methods: All patients 60 years or older with a primary hip...... fracture (ICD10: S720, S721, S722 and S729) were identified from 1 January 1995 to 31 December 2011. Hip fracture patients were matched 1:1 on age, gender and year of fracture to a non-hip fracture control. An individual's education attainment was defined as basic, secondary or higher, and their income was...... taken from their latest registered annual tax return (600,000 DKK). Poisson regression modeling was used to describe the association between income or education with rate of hip fracture, adjusting for confounders (smoking, alcohol, Charlson co-morbidity). Interactions were fitted between income and...

  10. Fracture analysis of ductile crack growth in weld material from a full-thickness clad RPV shell segment

    International Nuclear Information System (INIS)

    Evaluations of reactor pressure vessel (RPV) integrity under pressurized-thermal shock (PTS) loading are based on the Marshall flaw distribution, US Nuclear Regulatory Commission (NRC) Guide 1.154, and data from deep-crack fracture toughness specimens. Recent studies indicate that the onset of stable ductile tearing leads to crack-tip fields ahead of the growing crack and crack-tip profiles that differ from those of a stationary crack. Stable ductile tearing exposes additional volumes of material to elevated stresses as the crack advances, which alters the sampling of potential cleavage initiation sites on the microstructural level. Also, measured cleavage fracture toughness values for these specimens will be influenced by changes in crack-tip constraint conditions that occur with prior stable crack growth. Fracture analysis techniques for inclusion of ductile crack growth in finite-element analyses were evaluated through applications to a full-thickness clad beam specimen containing a shallow crack in material for which metallurgical conditions are prototypic of those found in RPVs at beginning of life. The beam specimen, which experienced a significant amount of precleavage stable ductile tearing, was fabricated from a section of an RPV wall (removed from a canceled nuclear plant) that includes weld, plate, and clad material. Effects of precleavage tearing on estimates of fracture toughness were investigated using continuum damage models

  11. The short transcript of Leishmania RNA virus is generated by RNA cleavage.

    Science.gov (United States)

    MacBeth, K J; Patterson, J L

    1995-01-01

    Leishmania RNA virus 1 produces a short viral RNA transcript corresponding to the 5' end of positive-sense single-stranded RNAs both in virally infected cells and in in vitro polymerase assays. We hypothesized that this short transcript was generated via cleavage of full-length positive-sense single-stranded RNA. A putative cleavage site was mapped by primer extension analysis to nucleotide 320 of the viral genome. To address the hypothesis that the short transcript is generated via cleavage at this site, two substrate RNAs that possessed viral sequence encompassing the putative cleavage site were created. When incubated with sucrose-purified viral particles, these substrate RNAs were site-specifically cleaved. The cleavage site of the in vitro-processed RNAs also mapped to viral nucleotide 320. The short-transcript-generating activity could be specifically abolished by proteinase K treatment of sucrose-purified viral particles and high concentrations of EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid], suggesting that the activity requires a proteinaceous factor and possibly intact viral particles. The cleavage activity is directly associated with short-transcript-generating activity, since only viral particle preparations which were capable of generating the short transcript in polymerase assays were also active in the cleavage assay. Furthermore, the short-transcript-generating activity is independent of the viral polymerase's transcriptase and replicase activities. We present a working model whereby cleavage of Leishmaniavirus RNA transcripts functions in the maintenance of a low-level persistent infection. PMID:7745692

  12. Proteolytic Cleavage of the Red Blood Cell Glycocalyx in a Genetic Form of Hypertension

    OpenAIRE

    Pot, Cécile; Chen, Angela Y.; Ha, Jessica N.; Schmid-Schönbein, Geert W

    2011-01-01

    Recent evidence suggests that the spontaneously hypertensive rat (SHR) has an elevated level of proteases, including matrix metalloproteinases (MMPs), involved in cell membrane receptor cleavage. We hypothesize that SHR red blood cells (RBCs) may be subject to an enhanced glycocalyx cleavage compared to the RBCs of the normotensive Wistar-Kyoto (WKY) rats. By direct observation of RBC rouleaux, we found no significant difference in RBC aggregation for unseparated SHR and WKY RBCs. However, li...

  13. Specific detection of the cleavage activity of mycobacterial enzymes using a quantum dot based DNA nanosensor

    Science.gov (United States)

    Jepsen, Morten Leth; Harmsen, Charlotte; Godbole, Adwait Anand; Nagaraja, Valakunja; Knudsen, Birgitta R.; Ho, Yi-Ping

    2015-12-01

    We present a quantum dot based DNA nanosensor specifically targeting the cleavage step in the reaction cycle of the essential DNA-modifying enzyme, mycobacterial topoisomerase I. The design takes advantages of the unique photophysical properties of quantum dots to generate visible fluorescence recovery upon specific cleavage by mycobacterial topoisomerase I. This report, for the first time, demonstrates the possibility to quantify the cleavage activity of the mycobacterial enzyme without the pre-processing sample purification or post-processing signal amplification. The cleavage induced signal response has also proven reliable in biological matrices, such as whole cell extracts prepared from Escherichia coli and human Caco-2 cells. It is expected that the assay may contribute to the clinical diagnostics of bacterial diseases, as well as the evaluation of treatment outcomes.We present a quantum dot based DNA nanosensor specifically targeting the cleavage step in the reaction cycle of the essential DNA-modifying enzyme, mycobacterial topoisomerase I. The design takes advantages of the unique photophysical properties of quantum dots to generate visible fluorescence recovery upon specific cleavage by mycobacterial topoisomerase I. This report, for the first time, demonstrates the possibility to quantify the cleavage activity of the mycobacterial enzyme without the pre-processing sample purification or post-processing signal amplification. The cleavage induced signal response has also proven reliable in biological matrices, such as whole cell extracts prepared from Escherichia coli and human Caco-2 cells. It is expected that the assay may contribute to the clinical diagnostics of bacterial diseases, as well as the evaluation of treatment outcomes. Electronic supplementary information (ESI) available: Characterization of the QD-based DNA Nanosensor. See DOI: 10.1039/c5nr06326d

  14. Engineering a ribozyme cleavage-induced split fluorescent aptamer complementation assay

    OpenAIRE

    Ausländer, Simon; Fuchs, David; Hürlemann, Samuel; Ausländer, David; Fussenegger, Martin

    2016-01-01

    Hammerhead ribozymes are self-cleaving RNA molecules capable of regulating gene expression in living cells. Their cleavage performance is strongly influenced by intra-molecular loop–loop interactions, a feature not readily accessible through modern prediction algorithms. Ribozyme engineering and efficient implementation of ribozyme-based genetic switches requires detailed knowledge of individual self-cleavage performances. By rational design, we devised fluorescent aptamer-ribozyme RNA archit...

  15. Spatial organization of topoisomerase I-mediated DNA cleavage induced by camptothecin–oligonucleotide conjugates

    OpenAIRE

    Arimondo, Paola B.; Angenault, Stéphane; Halby, Ludovic; Boutorine, Alexandre; Schmidt, Frédéric; Monneret, Claude; Garestier, Thérèse; Sun, Jian-Sheng; Bailly, Christian; Hélène, Claude

    2003-01-01

    Triple helix-forming oligonucleotides covalently linked to topoisomerase I inhibitors, in particular the antitumor agent camptothecin, trigger topoisomerase I-mediated DNA cleavage selectively in the proximity of the binding site of the oligonucleotide vector. In the present study, we have performed a systematic analysis of the DNA cleavage efficiency as a function of the positioning of the camptothecin derivative, either on the 3′ or the 5′ side of the triplex, and the location of the cleava...

  16. Nanorelief of the natural cleavage surface of triglycine sulphate crystals with substitutional and interstitial impurities

    International Nuclear Information System (INIS)

    Ferroelectric triglycine sulphate crystals (TGS) with substitutional (LADTGS+ADP, DTGS) and interstitial (Cr) impurities have been studied by atomic-force microscopy, X-ray diffraction, and X-ray fluorescence. The nanorelief parameters of the mirror cleavage TGS(010) surface have been measured with a high accuracy. A correlation between the crystal defect density in the bulk and the cleavage surface nanorelief is revealed at the submicrometer level.

  17. Reductive cleavage of dichalcogenide bonds. Communication 3. Selectivity of electron exchange in diaryldichalcogenide-bispyridinium systems

    International Nuclear Information System (INIS)

    The kinetics of reductive cleavage of the dichalcogenide bond in dimeric Schiff's bases ArEEAr (E = S, Te) induced by indirect electron transfer by the in situ generated bridged bispyridinium radical cations and biradicals was studied by cyclic voltammetry. It is found that the dependence between the apparent rate constants of intermolecular electron transfer and the electron-withdrawing properties of diaryldichalcogenides is violated. The mechanisms of homogeneous (chemical) and heterogeneous (electrochemical) reductive cleavage of diaryldichalcogenides are discussed

  18. A hingeless Fc fusion system for site-specific cleavage by IdeS.

    Science.gov (United States)

    Novarra, Shabazz; Grinberg, Luba; Rickert, Keith W; Barnes, Arnita; Wilson, Susan; Baca, Manuel

    2016-01-01

    Fusion of proteins to the Fc region of IgG is widely used to express cellular receptors and other extracellular proteins, but cleavage of the fusion partner is sometimes required for downstream applications. Immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) is a protease with exquisite specificity for human IgG, and it can also cleave Fc-fusion proteins at a single site in the N-terminal region of the CH2 domain. However, the site of IdeS cleavage results in the disulfide-linked hinge region partitioning with the released protein, complicating downstream usage of the cleaved product. To tailor the Fc fragment for release of partner proteins by IdeS treatment, we investigated the effect of deleting regions of IgG-derived sequence that are upstream of the cleavage site. Elimination of the IgG-derived hinge sequence along with several residues of the CH2 domain had negligible effects on expression and purity of the fusion protein, while retaining efficient processing by IdeS. An optimal Fc fragment comprising residues 235-447 of the human IgG1 heavy chain sufficed for efficient production of fusion proteins and minimized the amount of residual Ig-derived sequence on the cleavage product following IdeS treatment. Pairing of this truncated Fc fragment with IdeS cleavage enables highly specific cleavage of Fc-fusion proteins, thus eliminating the need to engineer extraneous cleavage sequences. This system should be helpful for producing Fc-fusion proteins requiring downstream cleavage, particularly those that are sensitive to internal miscleavage if treated with alternative proteases. PMID:27210548

  19. Evidence that Transcript Cleavage Is Essential for RNA Polymerase II Transcription and Cell Viability

    OpenAIRE

    Sigurdsson, Stefan; Dirac-Svejstrup, A. Barbara; Svejstrup, Jesper Q.

    2010-01-01

    Summary During transcript elongation in vitro, backtracking of RNA polymerase II (RNAPII) is a frequent occurrence that can lead to transcriptional arrest. The polymerase active site can cleave the transcript during such backtracking, allowing transcription to resume. Transcript cleavage is either stimulated by elongation factor TFIIS or occurs much more slowly in its absence. However, whether backtracking actually occurs in vivo, and whether transcript cleavage is important to escape it, has...

  20. Protein cleavage strategies for an improved analysis of the membrane proteome

    OpenAIRE

    Poetsch Ansgar; Fischer Frank

    2006-01-01

    Abstract Background Membrane proteins still remain elusive in proteomic studies. This is in part due to the distribution of the amino acids lysine and arginine, which are less frequent in integral membrane proteins and almost absent in transmembrane helices. As these amino acids are cleavage targets for the commonly used protease trypsin, alternative cleavage conditions, which should improve membrane protein analysis, were tested by in silico digestion for the three organisms Saccharomyces ce...

  1. Specific cleavage of human type III and IV collagens by Pseudomonas aeruginosa elastase.

    OpenAIRE

    Heck, L W; Morihara, K; McRae, W B; Miller, E J

    1986-01-01

    Purified Pseudomonas aeruginosa elastase cleaved human type III and IV collagens with the formation of specific cleavage products. Furthermore, type I collagen appeared to be slowly cleaved by both P. aeruginosa elastase and alkaline protease. These cleavage fragments from type III and IV collagens were separated from the intact collagen chains by SDS polyacrylamide gradient gel electrophoresis run under reducing conditions, and they were detected by their characteristic Coomassie blue staini...

  2. Association of polyadenylation cleavage factor I with U1 snRNP

    OpenAIRE

    Awasthi, Sita; Alwine, James C.

    2003-01-01

    Splicing and polyadenylation factors interact for the control of polyadenylation and the coupling of splicing and polyadenylation. We document an interaction between the U1 snRNP and mammalian polyadenylation cleavage factor I (CF Im), one of several polyadenylation factors needed for the cleavage of the pre-mRNA at the polyadenylation site. Sucrose density gradient centrifugation demonstrated that CF Im separated into two fractions, a light fraction which contained the known CF Im subunits (...

  3. CSNI Project for Fracture Analyses of Large-Scale International Reference Experiments (FALSIRE II)

    International Nuclear Information System (INIS)

    A summary of Phase II of the Project for FALSIRE is presented. FALSIRE was created by the Fracture Assessment Group (FAG) of the OECD/NEA's Committee on the Safety of Nuclear Installations (CNSI) Principal Working Group No. 3. FALSIRE I in 1988 assessed fracture methods through interpretive analyses of 6 large-scale fracture experiments in reactor pressure vessel (RPV) steels under pressurized- thermal-shock (PTS) loading. In FALSIRE II, experiments examined cleavage fracture in RPV steels for a wide range of materials, crack geometries, and constraint and loading conditions. The cracks were relatively shallow, in the transition temperature region. Included were cracks showing either unstable extension or two stages of extensions under transient thermal and mechanical loads. Crack initiation was also investigated in connection with clad surfaces and with biaxial load. Within FALSIRE II, comparative assessments were performed for 7 reference fracture experiments based on 45 analyses received from 22 organizations representing 12 countries. Temperature distributions in thermal shock loaded samples were approximated with high accuracy and small scatter bands. Structural response was predicted reasonably well; discrepancies could usually be traced to the assumed material models and approximated material properties. Almost all participants elected to use the finite element method

  4. Tensile deformation and fracture behavior of CuZn5 brass alloy at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Sharififar, M., E-mail: m.sharififar@ut.ac.ir; Akbari Mousavi, S.A.A., E-mail: akbarimusavi@ut.ac.ir

    2014-01-31

    Alpha brass alloys are widely used for production of rectangular waveguides because of their low bulk resistivity. In this paper, the microstructure, tensile deformation and fracture behavior of CuZn5 brass alloy were investigated. The strain rate sensitivity and its relation to post-uniform deformation in tensile test and correlation between strain hardening exponent (n) and temperature were examined. The results show that strain hardening exponent decreases from 0.5 to 0.4 with increase in test temperature from 250 to 450 °C. Tensile fracture mechanisms of as-extruded CuZn5 brass alloy were studied over a range of temperatures from 300 to 450 °C and range of strain rates from 0.01 to 0.4 1/s by means of scanning electron microscope (SEM) and Atomic Force Microscope (AFM). The results show that different fracture mechanisms operate in different temperature and strain rate ranges. While transgranular dimple fracture is dominant at 300 °C and 0.4 1/s, the dominant fracture mechanism at 450 °C and 0.01 1/s is cleavage facets. Precipitations and grain boundary sliding at high temperature may be the mechanism of ductility drop. Dynamic strain ageing (DSA) did not occur since none of the manifestations of DSA are observed.

  5. CSNI Project for Fracture Analyses of Large-Scale International Reference Experiments (FALSIRE II)

    Energy Technology Data Exchange (ETDEWEB)

    Bass, B.R.; Pugh, C.E.; Keeney, J. [Oak Ridge National Lab., TN (United States); Schulz, H.; Sievers, J. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Koeln (Gemany)

    1996-11-01

    A summary of Phase II of the Project for FALSIRE is presented. FALSIRE was created by the Fracture Assessment Group (FAG) of the OECD/NEA`s Committee on the Safety of Nuclear Installations (CNSI) Principal Working Group No. 3. FALSIRE I in 1988 assessed fracture methods through interpretive analyses of 6 large-scale fracture experiments in reactor pressure vessel (RPV) steels under pressurized- thermal-shock (PTS) loading. In FALSIRE II, experiments examined cleavage fracture in RPV steels for a wide range of materials, crack geometries, and constraint and loading conditions. The cracks were relatively shallow, in the transition temperature region. Included were cracks showing either unstable extension or two stages of extensions under transient thermal and mechanical loads. Crack initiation was also investigated in connection with clad surfaces and with biaxial load. Within FALSIRE II, comparative assessments were performed for 7 reference fracture experiments based on 45 analyses received from 22 organizations representing 12 countries. Temperature distributions in thermal shock loaded samples were approximated with high accuracy and small scatter bands. Structural response was predicted reasonably well; discrepancies could usually be traced to the assumed material models and approximated material properties. Almost all participants elected to use the finite element method.

  6. Golfer's fracture of the ribs

    International Nuclear Information System (INIS)

    Golfer's fracture is stress fracture of the posterior portion of left 3, 4, 5, 6 or 7th ribs of golfer's, usually beginners,and it is considered due to exposure to unaccustomed severe exercise of this fascinating sport. Healing is usually uneventful, but possible complication may occur, because symptom is mild and golfers continue the exercise with physical therapy such as massage. Author report 4 cases of golfer's fracture, including 1 case complicated by platelike at electasis of lung.

  7. Ultrasound evaluation of penile fractures

    OpenAIRE

    Kachewar, SG; Kulkarni, DS

    2011-01-01

    This short case report discusses the various aspects of penile fracture, which is a rare entity. Nevertheless, the incidence of penile fractures is on the rise due to the increased use of performance-enhancing drugs. An individual with a penile fracture should seek immediate medical referral. Prompt diagnosis and management is necessary to prevent undesirable after-effects as discussed. Emphasis is made on how imaging with ultrasound enables a quick and complete assessment of this mishap.

  8. Management of acetabular fractures: challenging work

    Institute of Scientific and Technical Information of China (English)

    CHEN Zheng-rong; YANG Yi

    2006-01-01

    @@ Acetabular fractures are complex and special intraarticular fractures. For most orthopaedic surgeons management of acetabular fractures is hard and challenging because the fractures are the results of high-energy trauma, and usually accompany with severe associated injuries. In addition, these fractures are uncommon except in a few trauma centers. The number of cases a surgeon can encounter is scarce.

  9. Management of parasymphyseal fractures of the mandible.

    Science.gov (United States)

    McClurg, F L

    1978-02-01

    Fractures of the parasymphyseal mandible occur in 15% of all cases of mandibular fracture. The experience obtained from 32 consecutive parasymphyseal fractures is outlined. Open reduction and internal fixation was required in patients having severe comminution, a mobile central fragment, or bilateral subcondylar fractures. These circumstances constituted 15% of all parasymphyseal fractures. The techniques utilized have been outlined. PMID:621994

  10. The role of the methyltransferase domain of bifunctional restriction enzyme RM.BpuSI in cleavage activity.

    Directory of Open Access Journals (Sweden)

    Arthur Sarrade-Loucheur

    Full Text Available Restriction enzyme (REase RM.BpuSI can be described as a Type IIS/C/G REase for its cleavage site outside of the recognition sequence (Type IIS, bifunctional polypeptide possessing both methyltransferase (MTase and endonuclease activities (Type IIC and endonuclease activity stimulated by S-adenosyl-L-methionine (SAM (Type IIG. The stimulatory effect of SAM on cleavage activity presents a major paradox: a co-factor of the MTase activity that renders the substrate unsusceptible to cleavage enhances the cleavage activity. Here we show that the RM.BpuSI MTase activity modifies both cleavage substrate and product only when they are unmethylated. The MTase activity is, however, much lower than that of M1.BpuSI and is thought not to be the major MTase for host DNA protection. SAM and sinefungin (SIN increase the Vmax of the RM.BpuSI cleavage activity with a proportional change in Km, suggesting the presence of an energetically more favorable pathway is taken. We further showed that RM.BpuSI undergoes substantial conformational changes in the presence of Ca(2+, SIN, cleavage substrate and/or product. Distinct conformers are inferred as the pre-cleavage/cleavage state (in the presence of Ca(2+, substrate or both and MTase state (in the presence of SIN and substrate, SIN and product or product alone. Interestingly, RM.BpuSI adopts a unique conformation when only SIN is present. This SIN-bound state is inferred as a branch point for cleavage and MTase activity and an intermediate to an energetically favorable pathway for cleavage, probably through increasing the binding affinity of the substrate to the enzyme under cleavage conditions. Mutation of a SAM-binding residue resulted in altered conformational changes in the presence of substrate or Ca(2+ and eliminated cleavage activity. The present study underscores the role of the MTase domain as facilitator of efficient cleavage activity for RM.BpuSI.

  11. Expression and in vitro cleavage activity of anti-caspase-7 hammerhead ribozymes

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Qing Xie; Xia-Qiu Zhou; Shan Jiang; You-Xin Jin

    2004-01-01

    AIM: To prepare hammerhead ribozymes against mouse caspase-7 and identify their cleavage activityin vitro, in order to select a ribozyme with specific cleavage activity against mouse caspase-7 as a potential gene therapy for apoptosis-related diseases.METHODS: Anti-caspase-7 ribozymes targeting sites 333and 394 (named Rz333 and Rz394) were designed by computer software, and their DNA sequences encoding ribozymes were synthesized. Caspase-7 DNA sequence was acquired by RT-PCR. Ribozymes and caspase-7 DNA obtained byin vitro transcription were cloned into pBSKneo U6' and pGEM-T vectors, respectively. The cleavage activity of ribozymes against mouse caspase-7 was identified by cleavage experimentsin vitro.RESULTS: Rz333 and Rz394 were designed and their DNA sequences were synthesized respectively. The expression vector of caspase-7 and plasmids containing Rz333 and Rz394 were reconstructed successfully. Ribozymes and caspase-7 mRNA were expressed byin vitro transcription.In vitro cleavage experiment showed that 243-nt and 744-nt segments were produced after caspase-7 mRNA was mixed with Rz333 in equivalent, and the cleavage efficiency was 67.98%. No cleaved segment was observed when caspase-7 mRNA was mixed with Rz394.CONCLUSION: Rz333 can site-specific cleave mouse caspase-7 mRNA, and it shows a potential for gene therapy of apoptosis-related diseases by down-regulating gene expression of caspase-7.

  12. Altered cleavage patterns in human tripronuclear embryos and their association to fertilization method

    DEFF Research Database (Denmark)

    Joergensen, Mette Warming; Agerholm, Inge; Hindkjaer, Johnny;

    2014-01-01

    stage (p < 0.001), and arrested development from the compaction stage and onwards (p < 0.001). For the IVF embryos, the 2nd and 3rd cleavage cycles were completed within the expected time frame. However, timing of the cell divisions within the cleavage cycles differed between the two groups. In contrast......, the completion of the 1st, 2nd, and 3rd cleavage cycle was delayed, but with a similar division pattern for 3PN ICSI compared with the 2PN ICSI embryos. 3PN, more often than 2PN ICSI embryos, displayed early cleavage into 3 cells (p = 0.03) and arrested development from the compaction stage and......PURPOSE: To analyze the cleavage patterns in dipronuclear (2PN) and tripronuclear (3PN) embryos in relation to fertilization method. METHOD: Time-lapse analysis. RESULTS: Compared to 2PN, more 3PN IVF embryos displayed early cleavage into 3 cells (p < 0.001), displayed longer duration of the 3-cell...

  13. Modelling fracture in ferritic steel

    CERN Document Server

    Smith, G

    2002-01-01

    Results from mathematical models and computer simulations of fracture in polycrystalline steels are presented for a range of temperatures. The proportions of intergranular and intragranular failure predicted are compared with experimental results for brittle fracture, ductile fracture and in the transition region. Interactive software to create two-dimensional polycrystalline models, which allow a range of physical to be varied independently, is described. The results include those for model materials chosen to match steels used by the power generation industry. The models simulate segregation and cavitation effects in steel and fracture of weldments and their associated heat-affected zones.

  14. Seismic characterization of fracture properties

    International Nuclear Information System (INIS)

    A critical component of site characterization and performance assessment involves the demonstration that any fluid flow which might reach the accessible environment is within acceptable limits. Various methods of analyzing flow in fractured rocks have been proposed, but choice of an appropriate method and its application to a specific site probably requires some knowledge of the spacing and length (or density) of fractures, their orientation and their hydraulic conductivity. Some of this information will undoubtedly come from geologic mapping on surface and in excavations, as well as from boreholes, cores and laboratory tests. However, it will be necessary to detect and characterize fractures in the rock mass between these direct observations. The remote detection and characterization of fractures by geophysical methods is, therefore, of considerable interest in connection with geologic repositories. The purpose of this paper is to show that there is a relationship, both empirical and theoretical, between the measured seismic response, the mechanical stiffness of fractures and their hydraulic conductivity. Laboratory measurements of the mechanical stiffness, hydraulic conductivity and seismic properties of natural fractures are summarized. A theoretical model for the amplitude and group time delay for compressional and shear waves transmitted across a single fracture is presented. Predictions based on this model are compared with laboratory measurements. Finally, the results for a single fracture are extended to multiple parallel fractures

  15. Hydraulic properties of fracture networks

    International Nuclear Information System (INIS)

    Fractured medium are studied in the general framework of oil and water supply and more recently for the underground storage of high level nuclear wastes. As fractures are generally far more permeable than the embedding medium, flow is highly channeled in a complex network of fractures. The complexity of the network comes from the broad distributions of fracture length and permeability at the fracture scale and appears through the increase of the equivalent permeability at the network scale. The goal of this thesis is to develop models of fracture networks consistent with both local-scale and global-scale observations. Bidimensional models of fracture networks display a wide variety of flow structures ranging from the sole permeable fracture to the equivalent homogeneous medium. The type of the relevant structure depends not only on the density and the length and aperture distributions but also on the observation scale. In several models, a crossover scale separates complex structures highly channeled from more distributed and homogeneous-like flow patterns at larger scales. These models, built on local characteristics and validated by global properties, have been settled in steady state. They have also been compared to natural well test data obtained in Ploemeur (Morbihan) in transient state. The good agreement between models and data reinforces the relevance of the models. Once validated and calibrated, the models are used to estimate the global tendencies of the main flow properties and the risk associated with the relative lack of data on natural fractures media. (author)

  16. Femoral shaft fractures

    International Nuclear Information System (INIS)

    The femur is the longest, largest, and strongest bone in the body. Because of its length, width, and role as primary weight-bearing bone, it must tolerate the extremes of axial loading and angulatory stresses. Massive musculature envelopes the femur. This masculature provides abundant blood supply to the bone, which also allows great potential for healing. Thus, the most significant problem relating to femoral shaft fractures is not healing, but restoration of bone length and alignment so that the femoral shaft will tolerate the functional stresses demanded of it

  17. [Rehabilitation after periprosthetic fractures].

    Science.gov (United States)

    Schmitt-Sody, M; Valle, C

    2016-03-01

    Periprosthetic fractures of the upper and lower extremities not only represent a challenge for surgeons but also for the rehabilitation team. The sometimes multimorbid patients have often undergone several surgical operations and need special planning and cooperation between an interdisciplinary team in order to achieve the best possible functional result and social reintegration. A structured rehabilitation planning after surgical treatment is a prerequisite for the patient to return to life as normal as possible. The aim is always rapid mobilization to achieve independence in activities of daily living. Special attention should be paid to postoperative immobilization and weight bearing. PMID:26923872

  18. Social economy partnerships and the public/private cleavages

    Directory of Open Access Journals (Sweden)

    Joxerramon Bengoetxea

    2012-06-01

    Full Text Available Public/Private Partnerships can be seen as one particular topos where the divide between the public domain, all levels of the Public Administration and the private initiative and private property is turned into a joint venture rather than a confrontation or a cleavage. Some of the possible combinations of public and private and where public/private partnerships might fit are displayed analytically. The importance of political theory or ideology in conceiving the relationships between ‘public’ and ‘private’, and the conceptions of a market economy as opposed to a social market economy cannot be exaggerated enough, but equally important are the legal or regulatory framework and the underlying dominant legal culture and legal principles, and of course the economic and financial situation. Public/private partnerships thrive in some conditions, but seem to wane in others, and the current predicament is not favourable, taking into account that only the regulatory framework is supportive of these ventures. Los partenariados público-privados se pueden entender como un espacio particular, en el que el sector público, todos los niveles de la administración pública, y la iniciativa privada y la propiedad privada, abordan una empresa conjunta, en lugar mantener posturas contrapuestas. Se muestran algunas de las posibles combinaciones del sector público y privado, en las que tendrían cabida los partenariados público/privados. Es patente la importancia de la teoría o la ideología política para entender las relaciones entre lo público y lo privado, y las concepciones de una economía de mercado frente a una economía social, pero tampoco se puede negar la importancia del marco legal o reglamentario y la cultura jurídica dominante subyacente, y los principios jurídicos, sin olvidar la situación económica y financiera. Los partenariados público-privados prosperan en algunas condiciones, pero no lo hacen siempre, y la situación econ

  19. Microstructural changes and fracture behavior of CF8M duplex stainless steels after long-term aging

    International Nuclear Information System (INIS)

    Microstructural changes and fracture behavior in cast CF8M duplex stainless steel after aging at 300-450 C for 300-10000 h have been investigated. Both, optical microscopical and transmission electron microscopical analyses, hardness and ferrite content measurements have been carried out in this study. Strengthening and aging phenomena of the ferrite phase have been identified by hardness measurements. Spinodal decomposition and heterogeneous precipitation of G-phase were found to be responsible for strengthening of the ferrite phase after aging with a temper parameter [P=log(t)+0.4343 Q/R(1/673.2-1/4)] (see Appendix A) in the range ca. 1.8-4.5. Three different fracture modes, dimples, cleavage and α/γ grain boundary separation, have been observed for Charpy V-notch and CT test specimens fractured at 20 C. (orig.)

  20. Phase II of the multinational project for fracture analysis of large-scale international reference experiments (FALSIRE II)

    International Nuclear Information System (INIS)

    This document describes the organization and plan for Phase II fo the Project for Fracture Analysis of Large-Scale International Reference Experiments (FALSIRE). The experiments employ a variety of test specimens, test materials, and loading conditions. The primary focus of the experiments was on the behaviour of relatively shallow cracks under conditions that relate to pressurized-thermal-shock loading in a reactor perssure vessel (RPV); the effects of biaxial loading and of cladding on cleavage fracture were separate topics of study in two experiments. A summary of each experiment is included in this report. Final versions of the problem statements will form the basis for FALSIRE II in which evaluations of the experiments will be performed by an international group of analysts using a variety of structural and fracture mechanis techniques. 7 refs, 7 figs, 5 tabs

  1. Gravity-Driven Hydraulic Fractures

    Science.gov (United States)

    Germanovich, L. N.; Garagash, D.; Murdoch, L. C.; Robinowitz, M.

    2014-12-01

    This study is motived by a new method for disposing of nuclear waste by injecting it as a dense slurry into a hydraulic fracture that grows downward to great enough depth to permanently isolate the waste. Disposing of nuclear waste using gravity-driven hydraulic fractures is mechanically similar to the upward growth of dikes filled with low density magma. A fundamental question in both applications is how the injected fluid controls the propagation dynamics and fracture geometry (depth and breadth) in three dimensions. Analog experiments in gelatin [e.g., Heimpel and Olson, 1994; Taisne and Tait, 2009] show that fracture breadth (the short horizontal dimension) remains nearly stationary when the process in the fracture "head" (where breadth is controlled) is dominated by solid toughness, whereas viscous fluid dissipation is dominant in the fracture tail. We model propagation of the resulting gravity-driven (buoyant or sinking), finger-like fracture of stationary breadth with slowly varying opening along the crack length. The elastic response to fluid loading in a horizontal cross-section is local and can be treated similar to the classical Perkins-Kern-Nordgren (PKN) model of hydraulic fracturing. The propagation condition for a finger-like crack is based on balancing the global energy release rate due to a unit crack extension with the rock fracture toughness. It allows us to relate the net fluid pressure at the tip to the fracture breadth and rock toughness. Unlike the PKN fracture, where breadth is known a priori, the final breadth of a finger-like fracture is a result of processes in the fracture head. Because the head is much more open than the tail, viscous pressure drop in the head can be neglected leading to a 3D analog of Weertman's hydrostatic pulse. This requires relaxing the local elasticity assumption of the PKN model in the fracture head. As a result, we resolve the breadth, and then match the viscosity-dominated tail with the 3-D, toughness

  2. Hydrologic behavior of fracture networks

    International Nuclear Information System (INIS)

    This paper reviews recent research on the nature of flow and transport in discontinuous fracture networks. The hydrologic behavior of these networks has been examined using two- and three-dimensional numerical models. The numerical models represent random realizations of fracture networks based on statistical field measurements of fracture geometry and equivalent hydraulic aperture. We have compared the flux and mechanical transport behavior of these networks to the behavior of equivalent continua. In this way we are able to determine whether a given fracture network can be modeled as an equivalent porous media in both flux and advective transport studies. We have examined departures from porous media behavior both as a function of interconnectivity and heterogeneity. Parameter studies have revealed behavior patterns such as: given a fracture frequency that can be measured in the field, porous media like behavior and the magnitude of permeability are both enhanced if the fractures are longer and the standard deviation of fracture permeabilities is smaller. Transport studies have shown that the ratio between flux and velocity is not necessarily constant when the direction of flow is changed in systems which do behave like a porous media for flux. Thus the conditions under which porous media analysis can be used in transport studies are more restrictive than the condition for flux studies. We have examined systems which do not behave like porous media and have shown how the in situ behavior varies as a function of scale of observation. The behavior of well tests in fractured networks has been modeled and compared to a new analytical well test solution which accounts for the early time dominance of the fractures intersecting the well. Finally, a three-dimensional fracture flow model has been constructed which assumes fractures are randomly located discs. 13 references, 12 figures

  3. Identification of BACE1 cleavage sites in human voltage-gated sodium channel beta 2 subunit

    Directory of Open Access Journals (Sweden)

    Kovacs Dora M

    2010-12-01

    Full Text Available Abstract Background The voltage-gated sodium channel β2 subunit (Navβ2 is a physiological substrate of BACE1 (β-site APP cleaving enzyme and γ-secretase, two proteolytic enzymes central to Alzheimer's disease pathogenesis. Previously, we have found that the processing of Navβ2 by BACE1 and γ-secretase regulates sodium channel metabolism in neuronal cells. In the current study we identified the BACE1 cleavage sites in human Navβ2. Results We found a major (147-148 L↓M, where ↓ indicates the cleavage site and a minor (144145 L↓Q BACE1 cleavage site in the extracellular domain of human Navβ2 using a cell-free BACE1 cleavage assay followed by mass spectrometry. Next, we introduced two different double mutations into the identified major BACE1 cleavage site in human Navβ2: 147LM/VI and 147LM/AA. Both mutations dramatically decreased the cleavage of human Navβ2 by endogenous BACE1 in cell-free BACE1 cleavage assays. Neither of the two mutations affected subcellular localization of Navβ2 as confirmed by confocal fluorescence microscopy and subcellular fractionation of cholesterol-rich domains. Finally, wildtype and mutated Navβ2 were expressed along BACE1 in B104 rat neuroblastoma cells. In spite of α-secretase still actively cleaving the mutant proteins, Navβ2 cleavage products decreased by ~50% in cells expressing Navβ2 (147LM/VI and ~75% in cells expressing Navβ2 (147LM/AA as compared to cells expressing wildtype Navβ2. Conclusion We identified a major (147-148 L↓M and a minor (144-145 L↓Q BACE1 cleavage site in human Navβ2. Our in vitro and cell-based results clearly show that the 147-148 L↓M is the major BACE1 cleavage site in human Navβ2. These findings expand our understanding of the role of BACE1 in voltage-gated sodium channel metabolism.

  4. Fractures of the Thoracic and Lumbar Spine

    Science.gov (United States)

    ... evaluate the spinal fracture pattern and decide whether spine surgery is needed. A CT scan taken from the ... the fracture falls through the disks of the spine, surgery should be performed to stabilize the fracture. AAOS ...

  5. Schizophrenia, antipsychotics and risk of hip fracture

    DEFF Research Database (Denmark)

    Sørensen, Holger J; Jensen, Signe O W; Nielsen, Jimmi

    2013-01-01

    (matched to 1:3 to schizophrenia controls without hip fracture), antipsychotic polypharmacy predicted hip fracture. Analyses among antipsychotic monotherapy patients showed no differential effect of individual antipsychotics. A dose-response relationship of hip fracture and lifetime antipsychotics...

  6. Pseudopathologic fracture of the femoral neck

    International Nuclear Information System (INIS)

    We have seen two cases of traumatic subcapital fractures of the femoral neck which resembled pathologic fractures on plain radiography. We have named this entity pseudopathologic fracture of the femoral neck and offer suggestions for why it occurs. (orig.)

  7. Image diagnosis of nasal bone fracture

    International Nuclear Information System (INIS)

    Twenty cases of nasal bone fractures were evaluated as to the types of fractures based upon HRCT findings. Conventional X-Ray films for nasal bones were analyzed and compared with HRCT findings. Nasal bone fractures were classified into lateral and frontal fractures. HRCT images were evaluated in three planes including upper, middle and lower portions of the nasal bone. Fractures favored males of teens. Lateral fracture gave rise to the fractures of the nasal bone opposite to the external force, loosening of the ipsilateral nasomaxillary sutures and fractures of the frontal process of the maxilla. Conventional X-Ray films were reevaluated after HRCT evaluation and indications of nasal bone fractures were determined. In addition to the discontinuity of the nasal dorsum, fracture lines parallel to and beneath the nasal dorsum and indistinct fracture lines along the nasomaxillary sutures are the indication of nasal bone fractures by conventional X-Ray films. (author)

  8. Photosensitized cleavage of dynein heavy chains. Cleavage at the V1 site by irradiation at 365 nm in the presence of ATP and vanadate

    Energy Technology Data Exchange (ETDEWEB)

    Gibbons, I.R.; Lee-Eiford, A.; Mocz, G.; Phillipson, C.A.; Tang, W.J.; Gibbons, B.H.

    1987-02-25

    Irradiation of soluble dynein 1 from sea urchin sperm flagella at 365 nm in the presence of MgATP and 0.05-50 microM vanadate (Vi) cleaves the alpha and beta heavy chains (Mr 428,000) at their V1 sites to give peptides of Mr 228,000 and 200,000, without the nonspecific side effects produced by irradiation at 254 nm as described earlier. The decrease in intact heavy chain material is biphasic; in 10 microM Vi, approximately 80% occurs with a half-time of 7 min and the remainder with a half-time of about 90 min, and the yield of cleavage peptides is better than 90%. Loss of dynein ATPase activity appears to be a direct result of the cleavage process and is not significantly affected by the presence of up to 0.1 M cysteamine (CA, 60-23-1) or 2-aminoethyl carbamimidothioic acid dihydrobromide (CA, 56-10-0) as free radical trapping agents. The concentration of Vi required for 50% maximal initial cleavage rate is 4.5 microM, while that for 50% ATPase inhibition is 0.8 microM, both in a 0.6 M NaCl medium. In the presence of 20 microM Vi, CTP and UTP support cleavage at about half the rate of ATP, whereas GTP and ITP support cleavage only if the Vi concentration is raised to about 200 microM. Substitution of any of the transition metal cations Cr2+, Mn2+, Fe2+, or Co2+ for the usual Mg2+ suppresses the photocleavage, presumably by quenching the excited chromophore prior to scission of the heavy chain. The photocleaved dynein 1 binds to dynein-depleted flagella similarly to intact dynein 1, but upon reactivation of the flagella with 1 mM ATP their motility is partially inhibited, rather than being augmented as with intact dynein.

  9. Fracture induced electromagnetic radiation

    International Nuclear Information System (INIS)

    In our laboratory, we combine accurate electromagnetic radiation (EMR) measurements during fracture of rocks (carbonate and igneous) and transparent materials (glass, PMMA and glass ceramics) with careful fractographic methods. A critical analysis of experimental observations, accumulated here during the last decade together with supporting material from the works of other authors are used in this study to demonstrate the failure of all current models to explain the properties of EMR arising from fracture. The basic elements of a new model are proposed. These are (a) the EMR amplitude increases as long as the crack continues to grow, since new atomic bonds are severed and their contribution is added to the EMR. As a result, the atoms on both sides of the bonds are moved to 'non-equilibrium' positions relative to their steady state ones and begin to oscillate collectively in a manner similar to Debye model bulk oscillations - 'surface vibrational optical waves'; (b) when the crack halts, the waves and the EMR pulse amplitude decay by relaxation. These basic elements are already enough to describe the characteristics of the experimentally obtained isolated individual EMR pulses. These characteristics include the shape of the EMR pulse envelope, and the frequency, time duration and rise - fall time of the pulse

  10. Degradation of impact fracture during accelerated aging of weld metal on microalloyed steel; Degradacion de la tenacidad al impacto durante el envejecimiento acelerado de soldadura en acero microaleado

    Energy Technology Data Exchange (ETDEWEB)

    Vargas-Arista, B.; Hallen, J. M.; Albiter, A.; Angeles-Chavez, C.

    2008-07-01

    The effect of accelerated aging on the toughness and fracture of the longitudinal weld metal on an API5L-X52 line pipe steel was evaluated by Charpy V-notch impact test, fracture analysis and transmission electron microscopy. Aging was performed at 250 degree centigrade for 100 to 1000 h. The impact results indicated a significant reduction in the fracture energy and impact toughness as a function of aging time, which were achieved by the scanning electron microscope fractography that showed a decrease in the vol fraction of microvoids by Charpy ductile failure with the aging time, which favored the brittle fracture by transgranular cleavage. The minimum vol fraction of microvoids was reached at 500 h due to the peak aged. The microstructural analysis indicated the precipitation of transgranular iron nano carbides in the aged specimens, which was related to the deterioration of toughness and change in the ductile to brittle behavior. (Author) 15 refs.

  11. A fracture mechanics analysis of the DCDC specimen

    International Nuclear Information System (INIS)

    The ''double cleavage drilled compression'' (DCDC) specimen is a rectangular bar with a circular hole in its centre that is loaded by compressive stresses. Due to the hole, positive stresses are generated in the vicinity that cause positive mode-I stress intensity factors. This specimen is used for the determination of crack growth under mode-I and in a modified version under mixed-mode loading conditions. A fracture mechanics analysis is presented on the basis of finite element computations. After compilation of literature results on mixed-mode stress intensity factors and T-stresses, weight functions for mode I and mode II are derived. The consequences of load misalignment and crack kinking are shown. Since stress intensity factor results from literature are available for long cracks compared with the hole radius only, also short-crack solutions are derived by use of the weight function technique. These results al-low to discuss the generation of the initial cracks necessary for fracture mechanics tests. In several papers, the side surface displacements were reported and discussed with respect to the occurrence of plasticity effects in glass. In order to decide whether deviations from the pure linear-elastic material behaviour are measured, it is necessary to know the elastic response. Therefore, a 3-dimensional finite element study is performed. It exhibits depression and uplifting of the free surface very similar to the re-sults found in literature

  12. Transverse Stress Fracture of the Proximal Patella

    OpenAIRE

    ATSUMI, SATORU; Arai, Yuji; Kato, Ko; Nishimura, Akinobu; Nakazora, Shigeto; Nakagawa, Shuji; Ikoma, Kazuya; Fujiwara, Hiroyoshi; Sudo, Akihiro; Kubo, Toshikazu

    2016-01-01

    Abstract Among stress fractures associated with sports activities, patellar stress fracture is rare. Regarding patella stress fractures, so far only distal transverse or lateral longitudinal fractures have been reported, but there are no reports of transverse fractures occurring in the proximal patella. We describe an extremely rare case of transverse stress fracture of proximal patella in a 9-year-old athlete. A 9-year old boy, who participated in sports (sprints and Kendo) presented with le...

  13. Application of small specimens to fracture mechanics characterization of irradiated pressure vessel steels

    International Nuclear Information System (INIS)

    In this study, precracked Charpy V-notch (PCVN) specimens were used to characterize the fracture toughness of unirradiated and irradiated reactor pressure vessel steels in the transition region by means of three-point static bending. Fracture toughness at cleavage instability was calculated in terms of elastic-plastic KJc values. A statistical size correction based upon weakest-link theory was performed. The concept of a master curve was applied to analyze fracture toughness properties. Initially, size-corrected PCVN data from A 533 grade B steel, designated HSST Plate O2, were used to position the master curve and a 5% tolerance bound for KJc data. By converting PCVN data to IT compact specimen equivalent KJc data, the same master curve and 5% tolerance bound curve were plotted against the Electric Power Research Institute valid linear-elastic KJc database and the ASME lower bound KIc curve. Comparison shows that the master curve positioned by testing several PCVN specimens describes very well the massive fracture toughness database of large specimens. These results give strong support to the validity of KJc with respect to KIc in general and to the applicability of PCVN specimens to measure fracture toughness of reactor vessel steels in particular. Finally, irradiated PCVN specimens of other materials were tested, and the results are compared to compact specimen data. The current results show that PCVNs demonstrate very good capacity for fracture toughness characterization of reactor pressure vessel steels. It provides an opportunity for direct measurement of fracture toughness of irradiated materials by means of precracking and testing Charpy specimens from surveillance capsules. However, size limits based on constraint theory restrict the operational test temperature range for KJc data from PCVN specimens. 13 refs., 8 figs., 1 tab

  14. Effects of consolidation temperature, strength and microstructure on fracture toughness of nanostructured ferritic alloys

    International Nuclear Information System (INIS)

    Fully consolidated nanostructured ferritic alloys (NFAs) were prepared by attritor milling pre-alloyed Fe-14Cr-3W-0.4Ti and 0.3 wt% Y2O3 powders, followed by hot isostatic pressing (HIPing) at 1000 oC or 1150 oC at 200 MPa for 4 h. Transmission electron microscopy (TEM) revealed similar bimodal distributions of fine and coarse ferrite grains in both cases. However, as expected, the alloy microhardness decreased with increasing in HIPing temperature. Three point bend tests on single edge notched specimens, with a nominal root radius ρ = 0.15 mm, were used to measure the notch fracture toughness, K ρ, as a function of test temperature. The K ρ curves were found to be similar for both processing conditions. It appears that the coarser ferrite grains control cleavage fracture, in a way that is independent of alloy strength and HIPing temperature

  15. Mechanical properties and fracture characteristics of high carbon steel after equal channel angular pressing

    International Nuclear Information System (INIS)

    The ultra-microduplex structure was fabricated in a fully pearlitic Fe–0.8 wt% C steel after equal channel angular pressing (ECAP) at 923 K via the Bc route. The microstructures and mechanical properties, before and after deformation, were investigated using scanning electron microscopy and mini-tensile tests. The cementite lamellae are gradually spheroidized by increasing the number of ECAP passes. After four passes, the cementite lamellae are fully spheroidized. Microhardness and the ultimate tensile strength of pearlite increase with the strain, up to a peak value (after two passes) and then decrease significantly. The yield strength, elongation and percentage of reduction in area increase with the number of ECAP passes. The tensile fracture morphology changes gradually from brittle cleavage to typical ductile fracture after four passes

  16. Theory and experiment on thermal shock fracture of initially corner-cracked nozzle

    International Nuclear Information System (INIS)

    The phenomenon of the pressurized thermal shock on the reactor pressure vessel is expected to occur in the case of such an accident as the small loss of the coolant accident in the PWR nuclear plant. In order to study the structural integrity of the reactor pressure vessel under the pressurized thermal shock, the cleavage thermal shock fracture experiment was conducted here using an initially corner-cracked nozzle type specimen made of the pressure vessel steel A508 class 3. The fracture mechanics analysis was performed to assess the crack behaviors in the experiment using the time dependent stress intensity factor deduced from the three-dimensional J integral with the thermal effect. (orig.)

  17. Deformation and fracture of LLM-105 molecular crystals studied by nanoindentation

    International Nuclear Information System (INIS)

    Mechanical deformation of crystalline high explosives plays an important role in both the fabrication of polymer-bonded explosives and controlling their sensitivity to mechanically-induced decomposition. Here, we study the deformation behavior of (010)-oriented LLM-105 and β-HMX molecular crystals by nanoindentation with pyramidal (Berkovich) and spherical (19 μm-diameter) indenters. Results reveal indentation elastic moduli of 21 and 18 GPa and Berkovich hardness of 0.73 and 0.65 GPa for LLM-105 and HMX, respectively. For LLM-105 (but not for HMX), indentation stress remains essentially unchanged for spherical indentation strains of ∼10–25%, suggesting that inelastic deformation above a certain strain proceeds via flow at constant stress. Both materials exhibit highly anisotropic surface fracture patterns after Berkovich and spherical indentation, consistent with fracture along (011) cleavage planes. No deformation-induced material decomposition is observed in either material for the indentation conditions used. (papers)

  18. Mechanical properties of fracture zones

    International Nuclear Information System (INIS)

    Available data on mechanical characteristics of fracture zones are compiled and discussed. The aim is to improve the basis for adequate representation of fracture zones in geomechanical models. The sources of data researched are primarily borehole investigations and case studies in rock engineering, involving observations of fracture zones subjected to artificial load change. Boreholes only yield local information about the components of fracture zones, i.e. intact rock, fractures and various low-strength materials. Difficulties are therefore encountered in evaluating morphological and mechanical properties of fracture zones from borehole data. Although often thought of as macroscopically planar features, available field data consistently show that fracture zones are characterized by geometrical irregularities such as thickness variations, surface undulation and jogs. These irregularities prevail on all scales. As a result, fracture zones are on all scales characterized by large, in-plane variation of strength- and deformational properties. This has important mechanical consequences in terms of non-uniform stress transfer and complex mechanisms of shear deformation. Field evidence for these findings, in particular results from the underground research laboratory in Canada and from studies of induced fault slip in deep mines, is summarized and discussed. 79 refs

  19. Mathematical modelling of fracture hydrology

    International Nuclear Information System (INIS)

    This report summarises the work performed between January 1983 and December 1984 for the CEC/DOE contract 'Mathematical Modelling of Fracture Hydrology', under the following headings: 1) Statistical fracture network modelling, 2) Continuum models of flow and transport, 3) Simplified models, 4) Analysis of laboratory experiments and 5) Analysis of field experiments. (author)

  20. Multiple fractures in early infancy

    International Nuclear Information System (INIS)

    Two cases of multiple fractures, one in a newborn with an unclassified bone dysplasia, another in an infant with recurrent fits of unknown etiology are reported. The second case is the youngest in the literature with bilateral slipped capital femoral epiphyses and bilateral femoral neck fractures, secondary to stress injury. (orig.)

  1. Epidemiological study on talus fractures

    Directory of Open Access Journals (Sweden)

    Marcos Hideyo Sakaki

    2014-08-01

    Full Text Available Objective:To analyze the characteristics of patients with talus fractures and the injuries that they present.Methods:Retrospective analysis on patients hospitalized in the Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine of the University of São Paulo, between 2006 and 2011, with talus fractures. Patient profile parameters, risk factors, fracture characteristics, treatment data and acute complications were analyzed.Results:Analysis on 23 cases showed that men were more affected than women, with a ratio of 4.8:1. The most frequent trauma mechanism was traffic accidents, followed by falls from a height. The most frequent type of fracture was at the neck of the talus, with 17 cases. Among the 23 cases, seven had peritalar dislocation at the time of presentation, four had exposed fractures and 11 presented other associated fractures. The mean length of time between the trauma and the definitive treatment was six days, while the mean length of hospital stay was 11 days. Three patients presented acute postoperative complications.Conclusion:Talus fractures occurred most commonly in the region of the talar neck and most frequently in young males who suffered high-energy trauma. In almost half of the cases, there were other associated fractures. The length of hospital stay was 11 days.

  2. Electrothermal fracturing of tensile specimens

    Science.gov (United States)

    Blinn, H. O.; Hanks, J. G.; Perkins, H. P.

    1970-01-01

    Pulling device consisting of structural tube, connecting rod, spring-loaded nuts, loading rod, heating element, and three bulkheads fractures tensile specimens. Alternate heating and cooling increases tensile loading by increments until fracturing occurs. Load cell or strain gage, applied to pulling rod, determines forces applied.

  3. Coronavirus 3CLpro proteinase cleavage sites: Possible relevance to SARS virus pathology

    Directory of Open Access Journals (Sweden)

    Blom Nikolaj

    2004-06-01

    Full Text Available Abstract Background Despite the passing of more than a year since the first outbreak of Severe Acute Respiratory Syndrome (SARS, efficient counter-measures are still few and many believe that reappearance of SARS, or a similar disease caused by a coronavirus, is not unlikely. For other virus families like the picornaviruses it is known that pathology is related to proteolytic cleavage of host proteins by viral proteinases. Furthermore, several studies indicate that virus proliferation can be arrested using specific proteinase inhibitors supporting the belief that proteinases are indeed important during infection. Prompted by this, we set out to analyse and predict cleavage by the coronavirus main proteinase using computational methods. Results We retrieved sequence data on seven fully sequenced coronaviruses and identified the main 3CL proteinase cleavage sites in polyproteins using alignments. A neural network was trained to recognise the cleavage sites in the genomes obtaining a sensitivity of 87.0% and a specificity of 99.0%. Several proteins known to be cleaved by other viruses were submitted to prediction as well as proteins suspected relevant in coronavirus pathology. Cleavage sites were predicted in proteins such as the cystic fibrosis transmembrane conductance regulator (CFTR, transcription factors CREB-RP and OCT-1, and components of the ubiquitin pathway. Conclusions Our prediction method NetCorona predicts coronavirus cleavage sites with high specificity and several potential cleavage candidates were identified which might be important to elucidate coronavirus pathology. Furthermore, the method might assist in design of proteinase inhibitors for treatment of SARS and possible future diseases caused by coronaviruses. It is made available for public use at our website: http://www.cbs.dtu.dk/services/NetCorona/.

  4. A Data Mining Approach for the Prediction of Hepatitis C Virus protease Cleavage Sites

    Directory of Open Access Journals (Sweden)

    Ahmed mohamed samir ali gamal eldin

    2011-12-01

    Full Text Available Summary: Several papers have been published about the prediction of hepatitis C virus (HCV polyprotein cleavage sites, using symbolic and non-symbolic machine learning techniques. The published papers achieved different Levels of prediction accuracy. the achieved results depends on the used technique and the availability of adequate and accurate HCV polyprotein sequences with known cleavage sites. We tried here to achieve more accurate prediction results, and more Informative knowledge about the HCV protein cleavage sites using Decision tree algorithm. There are several factors that can affect the overall prediction accuracy. One of the most important factors is the availably of acceptable and accurate HCV polyproteins sequences with known cleavage sites. We collected latest accurate data sets to build the prediction model. Also we collected another dataset for the model testing. Motivation: Hepatitis C virus is a global health problem affecting a significant portion of the world’s population. The World Health Organization estimated that in1999; 170 million hepatitis C virus (HCV carriers were present worldwide, with 3 to 4 million new cases per year. Several approaches have been performed to analyze HCV life cycle to find out the important factors of the viral replication process. HCV polyprotein processing by the viral protease has a vital role in the virus replication. The prediction of HCV protease cleavage sites can help the biologists in the design of suitable viral inhibitors. Results: The ease to use and to understand of the decision tree enabled us to create simple prediction model. We used here the latest accurate viral datasets. Decision tree achieved here acceptable prediction accuracy results. Also it generated informative knowledge about the cleavage process itself. These results can help the researchers in the development of effective viral inhibitors. Using decision tree to predict HCV protein cleavage sites achieved high

  5. A new strategy for the on-column exopeptidase cleavage of poly-histidine tagged proteins.

    Science.gov (United States)

    Kuo, Wen-Hui K; Chase, Howard A

    2011-10-15

    This paper describes a new strategy, which aims to make on-column poly-histidine tag removal more useful in the production of recombinant proteins by improving the yield and efficiency of on-column exopeptidase cleavage. This involves improvement of the on-column cleavage condition by using imidazole concentrations in the range of 100-500 mM in the cleavage buffer. At 300 mM imidazole, maximum on-column cleavage yield (in excess of 99%) was achieved in 3h of incubation. However, as a result of the increased imidazole concentration, this new strategy of on-column cleavage results in some residual uncleaved poly-histidine tagged proteins (~0.1%) and the production of cleaved dipeptides, both of which need to be further removed in a subsequent step. A method involving the recirculation of recovered proteins and peptides through the immobilized metal affinity chromatography (IMAC) column (same-column recirculation) was found to be superior to subtractive IMAC for the purpose of contaminant clearance. Recovery of the detagged target proteins was achieved using 10 column volumes of recovery buffer, which had the effect of diluting the imidazole concentration to a suitably low level for contaminant removal by same-column recirculation. This strategy was also applicable at a higher adsorbent loading of 10 mg protein/mL adsorbent with an optimal ratio of 200 mU of DAPase per mg of adsorbed tagged maltose binding protein (MBP), giving a cleavage yield of 99.1% in 3 h. Finally, on-column cleavage conditions including the effect of protease concentration and incubation time on the new strategy have been investigated and comparisons are made for different tag removal strategies. PMID:21925974

  6. Making the first fracture the last fracture: ASBMR task force report on secondary fracture prevention.

    Science.gov (United States)

    Eisman, John A; Bogoch, Earl R; Dell, Rick; Harrington, J Timothy; McKinney, Ross E; McLellan, Alastair; Mitchell, Paul J; Silverman, Stuart; Singleton, Rick; Siris, Ethel

    2012-10-01

    Fragility fractures are common, affecting almost one in two older women and one in three older men. Every fragility fracture signals increased risk of future fractures as well as risk of premature mortality. Despite the major health care impact worldwide, currently there are few systems in place to identify and "capture" individuals after a fragility fracture to ensure appropriate assessment and treatment (according to national guidelines) to reduce future fracture risk and adverse health outcomes. The Task Force reviewed the current evidence about different systematic interventional approaches, their logical background, as well as the medical and ethical rationale. This included reviewing the evidence supporting cost-effective interventions and developing a toolkit for reducing secondary fracture incidence. This report presents this evidence for cost-effective interventions versus the human and health care costs associated with the failure to address further fractures. In particular, it summarizes the evidence for various forms of Fracture Liaison Service as the most effective intervention for secondary fracture prevention. It also summarizes the evidence that certain interventions, particularly those based on patient and/or community-focused educational approaches, are consistently, if unexpectedly, ineffective. As an international group, representing 36 countries throughout Asia-Pacific, South America, Europe, and North America, the Task Force reviewed and summarized the international data on barriers encountered in implementing risk-reduction strategies. It presents the ethical imperatives for providing quality of care in osteoporosis management. As part of an implementation strategy, it describes both the quality improvement methods best suited to transforming care and the research questions that remain outstanding. The overarching outcome of the Task Force's work has been the provision of a rational background and the scientific evidence underpinning

  7. Conservative Management of Paediatric Clavicle Fractures

    Directory of Open Access Journals (Sweden)

    Barry J. O'Neill

    2011-01-01

    Full Text Available Paediatric clavicle fractures have traditionally been treated nonoperatively. Recent studies have recommended operative management for displaced midshaft fractures. We conducted a retrospective review of all clavicle fractures in children aged one to sixteen over a two-year period. We classified fractures and evaluated followup and clinical outcome. We identified 190 fractures. There were 135 boys and 55 girls. 65% of fractures were displaced and 35% undisplaced. Mean radiographic and clinical followup was 35 days and 44 days, respectively. Clavicle fractures in children heal with nonoperative management. Radiographs of clavicle fractures in children are unnecessary in the absence of clinical symptoms.

  8. Isolated Transverse Sacrum Fracture: A Case Report

    Directory of Open Access Journals (Sweden)

    Cemil Kavalci

    2011-01-01

    Full Text Available Sacral fracture commonly results from high-energy trauma. Most insufficiency fractures of the sacrum are seen in women after the age of 70. Fractures of the sacrum are rare and generally combined with a concomitant pelvic fracture. Transverse sacral fractures are even less frequent which constitute only 3–5% of all sacral fractures. This type of fractures provide a diagnostic challenge. We report a unique case of isolated transverse fracture of sacrum in a young man sustained low-energy trauma. The patient presented to our emergency department after several hours of injury, and diagnosed by clinical features and roentgenogram findings.

  9. Atypical fractures, a biased perspective.

    Science.gov (United States)

    Aspenberg, Per

    2016-01-01

    When stress fractures started to show up in the femurs of elderly ladies, it was soon evident that bisphosphonate use lay behind, and the absolute risk increase due to bisphosphonate use was reasonably well estimated already in 2008. Thereafter followed a period of confusion: the term atypical fracture was introduced, with a definition so vague that the true stress fractures tended to disappear in a cloud of ambiguity. This cast doubt on the association with bisphosphonates. The association was then re-established by large epidemiological studies based on radiographic adjudication. Atypical fractures are largely caused by bisphosphonates. With a correct indication, bisphosphonates prevent many more fractures than they cause, at least during the first years of use. With an incorrect indication they are likely to cause more harm than good. PMID:26768286

  10. Imaging of pelvic insufficiency fractures.

    Science.gov (United States)

    Peh, W C; Khong, P L; Yin, Y; Ho, W Y; Evans, N S; Gilula, L A; Yeung, H W; Davies, A M

    1996-03-01

    Insufficiency fractures of the pelvis are being increasingly recognized as a major cause of low back pain in elderly women with osteoporosis. Fractures in the sacrum are difficult to diagnose, as plain radiographic findings are either unhelpful or misleading. Bone scintigraphy is very sensitive for the detection of fractures in the sacrum, with demonstration of the H-shaped (or butterfly) sacral pattern or the combination of concomitant sacral and parasymphyseal uptake being considered as characteristic of insufficiency fractures. Computed tomography (CT) is helpful for confirming the presence of fractures in cases with atypical scintigraphic patterns, particularly in those with a known primary malignant neoplasm. CT is especially useful in the further evaluation of parasymphyseal and pubic rami lesions. The majority of patients respond well to periods of enforced bed rest and administration of analgesics. Recognition of the spectrum of imaging findings for this entity should lead to its correct identification and the institution of appropriate treatment. PMID:8966291

  11. Microfine grouting in tight fractures

    International Nuclear Information System (INIS)

    Microfine cements were used to grout tight fractures in basalt at McNary Dam in Umatilla, Oregon. Six boreholes were grouted with different microfine mixes. Hydraulic conductivity testing before and after the grouting provided a quantitative estimate of average fracture apertures and the effect of grouting on rock mass permeability. A downhole video camera survey was conducted in each hole to determine which fractures and joint sets allowed grout penetration. Pressure and the flow rate for grout were monitored during the testing. Total grout takes were calculated for each borehole stage grouted. Grouting pressures varied from less than a quarter to more than five times the estimated overburden pressure. The results of this testing indicate that tight fractures can be grouted with microfine cements. In addition, for tight fracture the relationship of injection pressures to grout take is significantly more non-linear than conventional grouting experience has suggested

  12. Distal clavicle fractures in children☆

    Science.gov (United States)

    Labronici, Pedro José; da Silva, Ricardo Rodrigues; Franco, Marcos Vinícius Viana; Labronici, Gustavo José; Pires, Robinson Esteves Santos; Franco, José Sergio

    2015-01-01

    Objective To analyze fractures of the distal clavicle region in pediatric patients. Methods Ten patients between the ages of five to eleven years (mean of 7.3 years) were observed. Nine patients were treated conservatively and one surgically. All the fractures were classified using the Nenopoulos classification system. Results All the fractures consolidated without complications. Conservative treatment was used for nine patients, of whom three were in group IIIB, three IIb, two IIa and one IV. The only patient who was treated surgically was a female patient of eleven years of age with a group IV fracture. Conclusion The treatment indication for distal fractures of the clavicle in children should be based on the patient's age and the displacement of the fragments. PMID:26962489

  13. Relative Permeability of Fractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Mark D. Habana

    2002-06-30

    Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.

  14. Effect of thermal ageing on the fracture behavior of EUROFER'97 steel

    International Nuclear Information System (INIS)

    Full text of publication follows: The low activation 9Cr-1W(V-Ta) EUROFER'97 steel has been accepted as a main structural material of tokamak blanket of prospective DEMO fusion power plant. The efficiency of proposed fusion reactors to the level suitable for energy production is predetermined by increase of temperature in tokamak vessel. The exploitation of EUROFER'97 steel at the temperatures close to 550 deg. C approaches limits of the steel usability. Microstructural changes causing embrittlement of EUROFER'97 steel are generally affected by synergy of thermal and radiation damage. The microstructural changes caused by thermal exposition and irradiation have been analysed in literature: i) irradiation causes formation of vacancies, H and He and Cr-rich α' phase and δ-Fe; ii) thermal exposition causes coarsening of carbides and segregation of P to grain boundaries, besides partially recrystallization to equiaxed ferrite grains. These two phenomena may cause the steel embrittlement and have to be investigated separately. The radiation damage and subsequent effect on mechanical properties has been analysed in literature as a preferred problem. Nevertheless the attention must be paid also to brittle fracture resistance of EUROFER'97 steel after thermal degradation. The aim of the paper has been to investigate physical principles that govern embrittlement of the EUROFER'97 steel in state after thermal ageing simulating the service conditions. The real thermal service conditions were simulated by using step-cooling treatment at temperatures from 650 deg. C to 520 deg. C and long term isothermal ageing at temperature 550 deg. C. The cleavage nucleation and brittle fracture initiation of the EUROFER'97 steel in as received and thermally aged state was analysed and described by means of the macroscopic fracture parameters and in addition, using local failure characteristics. The conditions of cleavage fracture nucleation and propagation across the grain boundary were

  15. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure

    International Nuclear Information System (INIS)

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of random grain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  16. Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bass, B.R.; McAfee, W.J.; Williams, P.T.; Pennell, W.E.

    1998-06-01

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states.

  17. Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

    International Nuclear Information System (INIS)

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states

  18. Distinct mechanisms for DNA cleavage by myoglobin with a designed heme active center.

    Science.gov (United States)

    Zhao, Yuan; Du, Ke-Jie; Gao, Shu-Qin; He, Bo; Wen, Ge-Bo; Tan, Xiangshi; Lin, Ying-Wu

    2016-03-01

    Heme proteins perform diverse biological functions, of which myoglobin (Mb) is a representative protein. In this study, the O2 carrier Mb was shown to cleave double stranded DNA upon aerobic dithiothreitol-induced reduction, which is fine-tuned by an additional distal histidine, His29 or His43, engineered in the heme active center. Spectroscopic (UV-vis and EPR) and inhibition studies suggested that free radicals including singlet oxygen and hydroxyl radical are responsible for efficient DNA cleavage via an oxidative cleavage mechanism. On the other hand, L29E Mb, with a distinct heme active center involving three water molecules in the met form, was found to exhibit an excellent DNA cleavage activity that was not depending on O2. Inhibition and ligation studies demonstrated for the first time that L29E Mb cleaves double stranded DNA into both the nicked circular and linear forms via a hydrolytic cleavage mechanism, which resembles native endonucleases. This study provides valuable insights into the distinct mechanisms for DNA cleavage by heme proteins, and lays down a base for creating artificial DNA endonucleases by rational design of heme proteins. Moreover, this study suggests that the diverse functions of heme proteins can be fine-tuned by rational design of the heme active center with a hydrogen-bonding network. PMID:26775281

  19. Characteristics of the fast electron emission produced during the cleavage of crystals

    Indian Academy of Sciences (India)

    B P Chandra; N L Patel; S S Rahangdale; R P Patel; V K Patle

    2003-01-01

    The present paper reports the fast electron emission produced during the cleavage of alkali halide crystals and models the dynamics of the process. The mechano-emission arises as a result of the ionization of surface traps at the expense of the energy which is released in the annihilation of the defects which are formed during cleavage. The slow electrons which appear upon the ionization of surface traps are subsequently accelerated in the field of negatively charged segment of the freshly cleaved surface. Considering the basic mechanism of fast electron emission, expressions are derived which are able to explain satisfactorily the temporal, thermal, charge, surface, coloration, water adsorption and other characteristics of the fast electron emission produced during the cleavage of crystals. The decay time of the charges on the newly created surfaces, and the velocity of cracks can be determined from the measurements of fast electron emission produced during the cleavage of crystals. It is shown that two types of diffusing centres are responsible for the charge relaxation and thereby for the emission of fast electrons produced during the cleavage of alkali halide crystals.

  20. Caspase cleavage sites in the human proteome: CaspDB, a database of predicted substrates.

    Directory of Open Access Journals (Sweden)

    Sonu Kumar

    Full Text Available Caspases are enzymes belonging to a conserved family of cysteine-dependent aspartic-specific proteases that are involved in vital cellular processes and play a prominent role in apoptosis and inflammation. Determining all relevant protein substrates of caspases remains a challenging task. Over 1500 caspase substrates have been discovered in the human proteome according to published data and new substrates are discovered on a daily basis. To aid the discovery process we developed a caspase cleavage prediction method using the recently published curated MerCASBA database of experimentally determined caspase substrates and a Random Forest classification method. On both internal and external test sets, the ranking of predicted cleavage positions is superior to all previously developed prediction methods. The in silico predicted caspase cleavage positions in human proteins are available from a relational database: CaspDB. Our database provides information about potential cleavage sites in a verified set of all human proteins collected in Uniprot and their orthologs, allowing for tracing of cleavage motif conservation. It also provides information about the positions of disease-annotated single nucleotide polymorphisms, and posttranslational modifications that may modulate the caspase cleaving efficiency.

  1. Focal adhesions control cleavage furrow shape and spindle tilt during mitosis

    Science.gov (United States)

    Taneja, Nilay; Fenix, Aidan M.; Rathbun, Lindsay; Millis, Bryan A.; Tyska, Matthew J.; Hehnly, Heidi; Burnette, Dylan T.

    2016-01-01

    The geometry of the cleavage furrow during mitosis is often asymmetric in vivo and plays a critical role in stem cell differentiation and the relative positioning of daughter cells during development. Early observations of adhesive cell lines revealed asymmetry in the shape of the cleavage furrow, where the bottom (i.e., substrate attached side) of the cleavage furrow ingressed less than the top (i.e., unattached side). This data suggested substrate attachment could be regulating furrow ingression. Here we report a population of mitotic focal adhesions (FAs) controls the symmetry of the cleavage furrow. In single HeLa cells, stronger adhesion to the substrate directed less ingression from the bottom of the cell through a pathway including paxillin, focal adhesion kinase (FAK) and vinculin. Cell-cell contacts also direct ingression of the cleavage furrow in coordination with FAs in epithelial cells—MDCK—within monolayers and polarized cysts. In addition, mitotic FAs established 3D orientation of the mitotic spindle and the relative positioning of mother and daughter centrosomes. Therefore, our data reveals mitotic FAs as a key link between mitotic cell shape and spindle orientation, and may have important implications in our understanding stem cell homeostasis and tumorigenesis. PMID:27432211

  2. Protein cleavage strategies for an improved analysis of the membrane proteome

    Directory of Open Access Journals (Sweden)

    Poetsch Ansgar

    2006-03-01

    Full Text Available Abstract Background Membrane proteins still remain elusive in proteomic studies. This is in part due to the distribution of the amino acids lysine and arginine, which are less frequent in integral membrane proteins and almost absent in transmembrane helices. As these amino acids are cleavage targets for the commonly used protease trypsin, alternative cleavage conditions, which should improve membrane protein analysis, were tested by in silico digestion for the three organisms Saccharomyces cerevisiae, Halobacterium sp. NRC-1, and Corynebacterium glutamicum as hallmarks for eukaryotes, archea and eubacteria. Results For the membrane proteomes from all three analyzed organisms, we identified cleavage conditions that achieve better sequence and proteome coverage than trypsin. Greater improvement was obtained for bacteria than for yeast, which was attributed to differences in protein size and GRAVY. It was demonstrated for bacteriorhodopsin that the in silico predictions agree well with the experimental observations. Conclusion For all three examined organisms, it was found that a combination of chymotrypsin and staphylococcal peptidase I gave significantly better results than trypsin. As some of the improved cleavage conditions are not more elaborate than trypsin digestion and have been proven useful in practice, we suppose that the cleavage at both hydrophilic and hydrophobic amino acids should facilitate in general the analysis of membrane proteins for all organisms.

  3. Two-step cleavage of hairpin RNA with 5' overhangs by human DICER

    Directory of Open Access Journals (Sweden)

    Suzuki Harukazu

    2011-02-01

    Full Text Available Abstract Background DICER is an RNase III family endoribonuclease that processes precursor microRNAs (pre-miRNAs and long double-stranded RNAs, generating microRNA (miRNA duplexes and short interfering RNA duplexes with 20~23 nucleotides (nts in length. The typical form of pre-miRNA processed by the Drosha protein is a hairpin RNA with 2-nt 3' overhangs. On the other hand, production of mature miRNA from an endogenous hairpin RNA with 5' overhangs has also been reported, although the mechanism for this process is unknown. Results In this study, we show that human recombinant DICER protein (rDICER processes a hairpin RNA with 5' overhangs in vitro and generates an intermediate duplex with a 29 nt-5' strand and a 23 nt-3' strand, which was eventually cleaved into a canonical miRNA duplex via a two-step cleavage. The previously identified endogenous pre-miRNA with 5' overhangs, pre-mmu-mir-1982 RNA, is also determined to be a substrate of rDICER through the same two-step cleavage. Conclusions The two-step cleavage of a hairpin RNA with 5' overhangs shows that DICER releases double-stranded RNAs after the first cleavage and binds them again in the inverse direction for a second cleavage. These findings have implications for how DICER may be able to interact with or process differing precursor structures.

  4. Caspase cleavage sites in the human proteome: CaspDB, a database of predicted substrates.

    Science.gov (United States)

    Kumar, Sonu; van Raam, Bram J; Salvesen, Guy S; Cieplak, Piotr

    2014-01-01

    Caspases are enzymes belonging to a conserved family of cysteine-dependent aspartic-specific proteases that are involved in vital cellular processes and play a prominent role in apoptosis and inflammation. Determining all relevant protein substrates of caspases remains a challenging task. Over 1500 caspase substrates have been discovered in the human proteome according to published data and new substrates are discovered on a daily basis. To aid the discovery process we developed a caspase cleavage prediction method using the recently published curated MerCASBA database of experimentally determined caspase substrates and a Random Forest classification method. On both internal and external test sets, the ranking of predicted cleavage positions is superior to all previously developed prediction methods. The in silico predicted caspase cleavage positions in human proteins are available from a relational database: CaspDB. Our database provides information about potential cleavage sites in a verified set of all human proteins collected in Uniprot and their orthologs, allowing for tracing of cleavage motif conservation. It also provides information about the positions of disease-annotated single nucleotide polymorphisms, and posttranslational modifications that may modulate the caspase cleaving efficiency. PMID:25330111

  5. Acute femoral neck fracture

    International Nuclear Information System (INIS)

    Ten patients with traumatic femoral neck fracture were studied with MR imaging (0.5 T, Magnetom, Siemens): unenhanced (multiecho, TR/TE = 1,600/30--240 [repetition time/echo time, msec]; gradient echo, TR/TE = 315/14, θ = 90 degrees) and Gd-DTPA enhanced (0.1 mM/kg body weight, Magnevist, Schering; gradient echo, TR/TE = 315/14, θ = 90 degrees). MR images were compared with clinical-radiographic findings. Digital subtraction angiography of the femoral head (FH) in five patients showed complete interruption of blood supply to the FH in three patients (signal intensity of FH did not increase on postcontrast images) and intact FH arteries in two patients (FH signal increased on postcontrast images, as did the healthy-side signal)

  6. Fracture flow code

    International Nuclear Information System (INIS)

    The hydrology of the SCV site will be modelled utilizing discrete fracture flow models. These models are complex, and can not be fully cerified by comparison to analytical solutions. The best approach for verification of these codes is therefore cross-verification between different codes. This is complicated by the variation in assumptions and solution techniques utilized in different codes. Cross-verification procedures are defined which allow comparison of the codes developed by Harwell Laboratory, Lawrence Berkeley Laboratory, and Golder Associates Inc. Six cross-verification datasets are defined for deterministic and stochastic verification of geometric and flow features of the codes. Additional datasets for verification of transport features will be documented in a future report. (13 figs., 7 tabs., 10 refs.) (authors)

  7. Scaphoid fracture associated with distal radius fracture in children:a case report

    Institute of Scientific and Technical Information of China (English)

    Hamdi Med Faouzi

    2009-01-01

    @@ Te forearm distal bone fracture is the most com-mon fracture in children. Scaphoid frac-ture is rare because the scaphoid is largely car-tilaginous in children. Some cases associating both distal radius and scaphoid fractures were reported in the literature. Scaphoid fracture often occurs without displacement and can be easily overlooked. We re-ported a case of children wrist injury combining scaphoid fracture with ipsilateral distal fracture.

  8. Non-Enzymatic DNA Cleavage Reaction Induced by 5-Ethynyluracil in Methylamine Aqueous Solution and Application to DNA Concatenation

    OpenAIRE

    Ikeda, Shuji; Tainaka, Kazuki; Matsumoto, Katsuhiko; Shinohara, Yuta; Koji L Ode; Susaki, Etsuo A; Ueda, Hiroki R

    2014-01-01

    DNA can be concatenated by hybridization of DNA fragments with protruding single-stranded termini. DNA cleavage occurring at a nucleotide containing a DNA base analogue is a useful method to obtain DNA with designed protruding termini. Here, we report a novel non-enzymatic DNA cleavage reaction for DNA concatenation. We found that DNA is cleaved at a nucleotide containing 5-ethynyluracil in a methylamine aqueous solution to generate 5′-phosphorylated DNA fragment as a cleavage product. We dem...

  9. Ratcheting of the substrate from the zymogen to proteinase conformations directs the sequential cleavage of prothrombin by prothrombinase

    OpenAIRE

    Bianchini, Elsa P.; Orcutt, Steven J.; Panizzi, Peter; Bock, Paul E.; Krishnaswamy, Sriram

    2005-01-01

    Prothrombinase catalyzes thrombin formation by the ordered cleavage of two peptide bonds in prothrombin. Although these bonds are likely ≈36 Å apart, sequential cleavage of prothrombin at Arg-320 to produce meizothrombin, followed by its cleavage at Arg-271, are both accomplished by equivalent exosite interactions that tether each substrate to the enzyme and facilitate presentation of the scissile bond to the active site of the catalyst. We show that impairing the conformational transition fr...

  10. Sequences downstream of AAUAAA signals affect pre-mRNA cleavage and polyadenylation in vitro both directly and indirectly.

    OpenAIRE

    Ryner, L C; Takagaki, Y; Manley, J L

    1989-01-01

    To investigate the role of sequences lying downstream of the conserved AAUAAA hexanucleotide in pre-mRNA cleavage and polyadenylation, deletions or substitutions were constructed in polyadenylation signals from simian virus 40 and adenovirus, and their effects were assayed in both crude and fractionated HeLa cell nuclear extracts. As expected, these sequences influenced the efficiency of both cleavage and polyadenylation as well as the accuracy of the cleavage reaction. Sequences near or upst...

  11. Restricted Active Site Docking by Enzyme-bound Substrate Enforces the Ordered Cleavage of Prothrombin by Prothrombinase*

    OpenAIRE

    Hacisalihoglu, Ayse; Panizzi, Peter; Bock, Paul E.; Camire, Rodney M.; Krishnaswamy, Sriram

    2007-01-01

    The preferred pathway for prothrombin activation by prothrombinase involves initial cleavage at Arg320 to produce meizothrombin, which is then cleaved at Arg271 to liberate thrombin. Exosite binding drives substrate affinity and is independent of the bond being cleaved. The pathway for cleavage is determined by large differences in Vmax for cleavage at the two sites within intact prothrombin. By fluorescence binding studies in the absence of catalysis, we have assessed the ability of the indi...

  12. The Role of the Methyltransferase Domain of Bifunctional Restriction Enzyme RM.BpuSI in Cleavage Activity

    OpenAIRE

    Arthur Sarrade-Loucheur; Shuang-yong Xu; Siu-Hong Chan

    2013-01-01

    Restriction enzyme (REase) RM.BpuSI can be described as a Type IIS/C/G REase for its cleavage site outside of the recognition sequence (Type IIS), bifunctional polypeptide possessing both methyltransferase (MTase) and endonuclease activities (Type IIC) and endonuclease activity stimulated by S-adenosyl-L-methionine (SAM) (Type IIG). The stimulatory effect of SAM on cleavage activity presents a major paradox: a co-factor of the MTase activity that renders the substrate unsusceptible to cleavag...

  13. In vitro cleavage of the simian virus 40 early polyadenylation site adjacent to a required downstream TG sequence.

    OpenAIRE

    Sperry, A O; Berget, S M

    1986-01-01

    Exogenous RNA containing the simian virus 40 early polyadenylation site was efficiently and accurately polyadenylated in in vitro nuclear extracts. Correct cleavage required ATP. In the absence of ATP, nonpoly(A)+ products accumulated which were 18 to 20 nucleotides longer than the RNA generated by correct cleavage; the longer RNA terminated adjacent to the downstream TG element required for polyadenylation. In the presence of ATP analogs, alternate cleavage was not observed; instead, correct...

  14. Fracture toughness anisotropy in shale

    Science.gov (United States)

    Chandler, Michael R.; Meredith, Philip G.; Brantut, Nicolas; Crawford, Brian R.

    2016-03-01

    The use of hydraulic fracturing to recover shale gas has focused attention on the fundamental fracture properties of gas-bearing shales, but there remains a paucity of available experimental data on their mechanical and physical properties. Such shales are strongly anisotropic, so that their fracture propagation trajectories depend on the interaction between their anisotropic mechanical properties and the anisotropic in situ stress field in the shallow crust. Here we report fracture toughness measurements on Mancos shale determined in all three principal fracture orientations: Divider, Short Transverse, and Arrester, using a modified short-rod methodology. Experimental results for a range of other sedimentary and carbonate rocks are also reported for comparison purposes. Significant anisotropy is observed in shale fracture toughness measurements at ambient conditions, with values, as high as 0.72 MPa m1/2 where the crack plane is normal to the bedding, and values as low as 0.21 MPa m1/2 where the crack plane is parallel to the bedding. For cracks propagating nonparallel to bedding, we observe a tendency for deviation toward the bedding-parallel orientation. Applying a maximum energy release rate criterion, we determined the conditions under which such deviations are more or less likely to occur under more generalized mixed-mode loading conditions. We find for Mancos shale that the fracture should deviate toward the plane with lowest toughness regardless of the loading conditions.

  15. MR imaging of occult fractures

    International Nuclear Information System (INIS)

    Objective: To investigate the value of MR imaging in detecting occult fractures. Methods: Sixteen cases with acute trauma were studied using radiography and MR imaging, three cases also underwent CT examinations. Three fractures occurred in the femur condyle, 8 in the proximal tibia and 5 in the thoracolumbar spine. Results: All sixteen cases had normal radiographic results. In 11 cases with femur condyle and tibia occult fracture, MR imaging demonstrated linear low signal in the subcortical region in 3 cases and irregular low signal from articular faces to shaft in 8 cases on both T1WI and T2WI, and high signal changes around low signal were seen on T2WI, and the width of low signal was less than 4 mm on both T1WI and T2WI. The high signal in T1 weighted-Fat saturated sequence was more remarkable and wider than that on T2WI. 3 cases with CT scanning showed no fracture signs. In five cases with thoracolumbar vertebral occult fractures, MR imaging demonstrated horizontal linear low signal in the center of vertebra on both T1WI and T2WI, and high signal changes around low signal were seen on T2WI. Conclusions: MR imaging could early determine the diagnosis of occult fractures. MRI should be the next examination of choice when plain films fail to reveal suspected fractures in the setting of suggestive symptoms and positive physical examination

  16. Rib fracture: Different radiographic projections

    International Nuclear Information System (INIS)

    Rib fracture is the most common thoracic injury. It is thought to be present in 10% of all traumatic injuries and in almost 40% of patients who sustained severe non-penetrating trauma. There are 12 pairs of ribs. This study reviews various methods of acquisition and reconstruction of radiographic images of traumatic rib fractures in order to determine the optimal views and to simplify rib fracture diagnostics. Eight different plain radiography pictures of ribs were performed with the patient in an erect position. The following projections were obtained in sequence: oblique at 45° or 30° angle on inspiration, oblique at 45° or 30° angle on expiration as well as 45° and 39° projections during slow and fast breathing. All radiographic examinations were performed using a Philips three-phase scanner installed at the Al- Razi Hospital in Jenin, Palestine. The results demonstrate that the 45° antero-posterior oblique projection performed on expiration is recommended for diagnostics and interpretation of traumatic rib fractures. Conclusion emerging from this study are such that for a 45° oblique view on expiration is recommended for radiographic imaging of patients with clinical signs of fracture, e.g. evaluation of lower rib fractures, while 45° oblique view during fast breathing is recommended for suspected upper rib fractures

  17. Early history of scapular fractures.

    Science.gov (United States)

    Bartoníček, Jan; Kozánek, Michal; Jupiter, Jesse B

    2016-01-01

    The first to use the term Scapula was Vesalius (1514-1564) and thus it has remained ever since. Probably the oldest injured scapula, from 250 million years ago, was described by Chinese authors of a skeletal examination of a fossilised remains of a dinosaur Yangchuanosaurus hepingensis. In humans, the oldest known scapular fractures date back to the prehistoric and early historic times. In ancient times, a fracture of acromion was described in the treatises of Hippocrates. Early modern history of the treatment of scapular fractures is closely interlinked with the history of the French surgery. The first to point out the existence of these fractures were Petit, Du Verney and Desault in the 18th century. The first study devoted solely to scapular fractures was published by Traugott Karl August Vogt in 1799. Thomas Callaway published in 1849 an extensive dissertation on injuries to the shoulder girdle, in which he discussed a number of cases known at that time. The first radiograph of a scapular fracture was published by Petty in 1907. Mayo Robson (1884), Lambotte (1913) and Lane (1914) were pioneers in the surgical treatment of these fractures, followed in 1923 by the French surgeons Lenormat, Dujarrier and Basset. The first internal fixation of the glenoid fossa, including a radiograph, was published by Fischer in 1939. PMID:26133287

  18. In Situ Raman Monitoring of Silver(I)-Aided Laser-Driven Cleavage Reaction of Cyclobutane.

    Science.gov (United States)

    Chen, Dengtai; Han, Xijiang; Du, Yunchen; Wang, Hsing-Lin; Xu, Ping

    2016-01-01

    The cyclobutane cleavage reaction is an important process and has received continuous interest. Herein, we demonstrate the visible laser-driven cleavage reaction of cyclobutane in crystal form by using in situ Raman spectroscopy. Silver(I) coordination-induced strain and thermal effects from the laser irradiation are the two main driving forces for the cleavage of cyclobutane crystals. This work may open up a new avenue for studying cyclobutane cleavage reactions, as compared to the conventional routes using ex situ techniques. PMID:26510491

  19. Identification of RNA sequences and structures involved in site-specific cleavage of IGF-II mRNAs.

    OpenAIRE

    van Dijk, E L; Sussenbach, J S; Holthuizen, P E

    1998-01-01

    Insulin-like growth factor-II (IGF-II) mRNAs are subject to site-specific endonucleolytic cleavage in the 3' untranslated region (UTR), rendering an unstable 5' cleavage product containing the coding region and a very stable 3' cleavage product of 1.8 kb consisting of the 3'-UTR sequence and the poly(A) tail. Previously, it was established that two widely separated elements in the 3'-UTR (elements I and II), that can form a duplex structure, are necessary and sufficient for cleavage. To furth...

  20. Age hardening, fracture behavior and mechanical properties of QE22 Mg alloy

    Directory of Open Access Journals (Sweden)

    F. Khan MD

    2015-09-01

    Full Text Available The microstructure, mechanical properties and fracture behavior of an as-received QE22 alloy have been investigated under different thermal conditions, including solution treated (ST, under aged (UA, peak aged (PA and over aged (OA conditions. A significant increase in hardness of 27%, yield strength of 60% and ultimate tensile strength of 19% was observed in peak aged sample as compared to solution treated sample. The improvements of mechanical strength properties are mainly associated with the metastable λ and β′ precipitates. Grain growth was not observed in the ST samples after subjecting to UA and PA treatments due to the presence of eutectic Mg12Nd particles along the grain boundaries. In over aged sample, significant grain growth occurred because of dissolution of eutectic phase particles. Different natures of crack initiation and propagation were observed under different thermal conditions during tensile testing at room temperature. The mode of failure of solution treated sample is transgranular, cleavage and twin boundary fractures. A mixed mode of transgranular, intergranular, cleavage and twin boundary failure is observed in both peak aged and over aged samples.